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Sample records for solar p-mode frequencies

  1. High sensitivity of p-modes near the acoustic cutoff frequency to solar model parameters

    NASA Technical Reports Server (NTRS)

    Guenther, D. B.

    1991-01-01

    The p-mode frequencies of low l have been calculated for solar models with initial helium mass fraction varying from Y = 0.2753-0.2875. The differences in frequency of the p-modes in the frequency range, 2500-4500 microHz, do not exceed 1-5 microHz among the models. But in the vicinity of the acoustic cutoff frequency, near 5000 microHz the p-mode frequency differences are enhanced by a factor of 4. The enhanced sensitivity of p-modes near the acoustic cutoff frequency was further tested by calculating and comparing p-mode frequencies of low l for two solar models one incorporating the Eddington T-tau relation and the other the Krishna Swamy T-tau relation. Again, it is found that p-modes with frequencies near the acoustic cutoff frequency show a significant increase in sensitivity to the different T-tau relations, compared to lower frequency p-modes. It is noted that frequencies above the acoustic cutoff frequency are complex, hence, cannot be modeled by the adiabatic pulsation code (assumes real eigenfrequencies) used in these calculations.

  2. Nonadiabatic nonradial p-mode frequencies of the standard solar model, with and without helium diffusion

    NASA Technical Reports Server (NTRS)

    Guenther, D. B.

    1994-01-01

    The nonadiabatic frequencies of a standard solar model and a solar model that includes helium diffusion are discussed. The nonadiabatic pulsation calculation includes physics that describes the losses and gains due to radiation. Radiative gains and losses are modeled in both the diffusion approximation, which is only valid in optically thick regions, and the Eddington approximation, which is valid in both optically thin and thick regions. The calculated pulsation frequencies for modes with l less than or equal to 1320 are compared to the observed spectrum of the Sun. Compared to a strictly adiabatic calculation, the nonadiabatic calculation of p-mode frequencies improves the agreement between model and observation. When helium diffusion is included in the model the frequencies of the modes that are sensitive to regions near the base of the convection zone are improved (i.e., brought into closer agreement with observation), but the agreement is made worse for other modes. Cyclic variations in the frequency spacings of the Sun as a function of frequency of n are presented as evidence for a discontinuity in the structure of the Sun, possibly located near the base of the convection zone.

  3. Constancy of intermediate-degree p-mode frequencies during the declining phase of solar cycle 21

    SciTech Connect

    Rhodes, E.J. Jr.; Woodard, M.F.; Cacciani, A.; Tomczyk, S.; Korzennik, S.G.

    1988-03-01

    A comparison was made between two sets of frequencies of intermediate-degree solar p-mode oscillations obtained in late 1981 and mid-1984. Good agreement was found at the 0.02 microHz level despite the 2.6 yr interval separating the two sets of observations. In particular, a comparison was made between the frequencies of 573 modes obtained at the South Pole during December 24-25, 1981 and those of the same modes as observed at the Mount Wilson Observatory 60-ft Solar Tower during July 29-August 13, 1984. The present results are consistent with no change in intermediate-degree p-mode frequencies between late 1981 and mid-1985. 17 references.

  4. On the constancy of intermediate-degree p-mode frequencies during the declining phase of solar cycle 21

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Woodard, Martin F.; Cacciani, Alessandro; Tomczyk, Steven; Korzennik, Sylvain G.

    1988-01-01

    A comparison was made between two sets of frequencies of intermediate-degree solar p-mode oscillations obtained in late 1981 and mid-1984. Good agreement was found at the 0.02 microHz level despite the 2.6 yr interval separating the two sets of observations. In particular, a comparison was made between the frequencies of 573 modes obtained at the South Pole during December 24-25, 1981 and those of the same modes as observed at the Mount Wilson Observatory 60-ft Solar Tower during July 29-August 13, 1984. The present results are consistent with no change in intermediate-degree p-mode frequencies between late 1981 and mid-1985.

  5. solarFLAG hare and hounds: estimation of p-mode frequencies from Sun-as-star helioseismology data

    NASA Astrophysics Data System (ADS)

    Jiménez-Reyes, S. J.; Chaplin, W. J.; García, R. A.; Appourchaux, T.; Baudin, F.; Boumier, P.; Elsworth, Y.; Fletcher, S. T.; Lazrek, M.; Leibacher, J. W.; Lochard, J.; New, R.; Régulo, C.; Salabert, D.; Toutain, T.; Verner, G. A.; Wachter, R.

    2008-10-01

    We report on the results of the latest solarFLAG hare-and-hounds exercise, which was concerned with testing methods for extraction of frequencies of low-degree solar p modes from data collected by Sun-as-a-star observations. We have used the new solarFLAG simulator, which includes the effects of correlated mode excitation and correlations with background noise, to make artificial time-series data that mimic Doppler velocity observations of the Sun-as-a-star. The correlations give rise to asymmetry of mode peaks in the frequency power spectrum. 10 members of the group (the hounds) applied their `peak-bagging' codes to a 3456-d data set, and the estimated mode frequencies were returned to the hare (who was WJC) for comparison. Analysis of the results reveals a systematic bias in the estimated frequencies of modes above ~1.8mHz. The bias is negative, meaning the estimated frequencies systematically underestimate the input frequencies. We identify two sources that are the dominant contributions to the frequency bias. Both sources involve failure to model accurately subtle aspects of the observed power spectral density in the part (window) of the frequency power spectrum that is being fitted. One source of bias arises from a failure to account for the power spectral density coming from all those modes whose frequencies lie outside the fitting windows. The other source arises from a failure to account for the power spectral density of the weak l = 4 and 5 modes, which are often ignored in Sun-as-a-star analysis. The Sun-as-a-star peak-bagging codes need to allow for both sources, otherwise the frequencies are likely to be biased.

  6. Initial high-degree p-mode frequency splittings from the 1988 Mt. Wilson 60-foot Tower Solar Oscillation Program

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain G.

    1988-01-01

    The initial frequency splitting results of solar p-mode oscillations obtained from the 1988 helioseismology program at the Mt. Wilson Observatory are presented. The frequency splittings correspond to the rotational splittings of sectoral harmonics which range in degree between 10 and 598. They were obtained from a cross-correlation analysis of the prograde and retrograde portions of a two-dimensional (t - v) power spectrum. This power spectrum was computed from an eight-hour sequence of full-disk Dopplergrams obtained on July 2, 1988, at the 60-foot tower telescope with a Na magneto-optical filter and a 1024x1024 pixel CCD camera. These frequency splittings have an inherently larger scatter than did the splittings obtained from earlier 16-day power spectra. These splittings are consistent with an internal solar rotational velocity which is independent of radius along the equatorial plane. The normalized frequency splittings averaged 449 + or - 3 nHz, a value which is very close to the observed equatorial rotation rate of the photospheric gas of 451.7 nHz.

  7. Solar p-Modes Modulated by Interior g-Modes

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing

    2001-08-01

    The process by which frequency modulations of solar p-modes with shorter periods (~5 minutes) occur because of the presence of solar interior g-modes with longer periods (greater than a few hours approximately) is studied. The key results of a model analysis are given. In addition to the effects of stochastic excitation, this modulation by g-modes would give rise to fine spectral structures in the form of frequency sideband peaks closely packed around individual p-modes (with narrow frequency intervals on the order of g-mode frequencies) rather than of separate g-mode spectral power peaks in the low-frequency bands. For those p-modes of low degree that penetrate deep into the solar interior, this effect of frequency modulation by interior g-modes (if they exist) should be more pronounced. Observationally, individual p-modes usually contain numerous fine peaks that have to be somehow modeled (or smoothed) in order to estimate p-mode frequencies, amplitudes, and line widths, etc. By carefully weeding out noises of various origins in high-resolution p-mode frequency spectra, one might be able to extract the desired signals of g-modes trapped in the solar interior that have so far evaded the scrutiny of advanced helioseismological experiments.

  8. A Comparison of Solar p-Mode Parameters from MDI and Gong: Mode Frequencies and Structure Inversions

    NASA Technical Reports Server (NTRS)

    Basu, S.; Christensen-Dalsgaard, J.; Howe, R.; Schou, J.; Thompson, M. J.; Hill, F.; Komm, R.

    2003-01-01

    Helioseismic analysis of solar global oscillations allows investigation of the internal structure of the Sun. One important test of the reliability of the inferences from helioseismology is that the results from independent sets of contemporaneous data are consistent with one another. Here we compare mode frequencies from the Global Oscillation Network Group and Michelson Doppler Imager on board SOHO and resulting inversion results on the Sun's internal structure. The average relative differences between the data sets are typically less than 1 x 10(exp -5) substantially smaller than the formal errors in the differences; however, in some cases the frequency differences show a systematic behavior that might nonetheless influence the inversion results. We find that the differences in frequencies are not a result of instrumental effects but are almost entirely related to the data pipeline software. Inversion of the frequencies shows that their differences do not result in any significant effects on the resulting inferences on solar structure. We have also experimented with fitting asymmetric profiles to the oscillation power spectra and find that, compared with the symmetric fits, this causes no significant change in the inversion results.

  9. Solar p modes in 10 years of the IRIS network

    NASA Astrophysics Data System (ADS)

    Salabert, D.; Fossat, E.; Gelly, B.; Kholikov, S.; Grec, G.; Lazrek, M.; Schmider, F. X.

    2004-01-01

    IRIS data (the low degree ℓ≤ 3 helioseismology network) have been analysed for the study of p-mode parameters variability over the falling phase of the solar activity cycle 22 and the rising phase of the solar activity cycle 23. The IRIS duty cycle has been improved by the so-called ``repetitive music method'', a method of partial gap filling. We present in this paper an analysis of the dependence of p-mode frequencies and linewidths with frequency and with solar magnetic activity. We confirm also the periodicity of about 70 μHz of the high-frequency pseudo modes, with a much reduced visibility during the phase of higher activity.

  10. A new efficient method for determining weighted power spectra: detection of low-frequency solar p-modes by analysis of BiSON data

    NASA Astrophysics Data System (ADS)

    Fletcher, S. T.; Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; New, R.

    2011-08-01

    We present a new and highly efficient algorithm for computing a power spectrum made from evenly spaced data which combines the noise-reducing advantages of the weighted fit with the computational advantages of the fast Fourier transform. We apply this method to a 10-yr data set of the solar p-mode oscillations obtained by the Birmingham Solar Oscillations Network (BiSON) and thereby uncover three new low-frequency modes. These are the ℓ= 2, n= 5 and n= 7 modes and the ℓ= 3, n=7 mode. In the case of the ℓ= 2, n= 5 mode, this is believed to be the first such identification of this mode in the literature. The statistical weights needed for the method are derived from a combination of the real data and a sophisticated simulation of the instrument performance. Variations in the weights are due mainly to the differences in the noise characteristics of the various BiSON instruments, the change in those characteristics over time and the changing line-of-sight velocity between the stations and the Sun. It should be noted that a weighted data set will have a more time-dependent signal than an unweighted set and that, consequently, its frequency spectrum will be more susceptible to aliasing.

  11. Excitation of solar p-modes

    NASA Technical Reports Server (NTRS)

    Goldreich, Peter; Murray, Norman; Kumar, Pawan

    1994-01-01

    We investigate the rates at which energy is supplied to individual p-modes as a function of their frequencies nu and angular degrees l. The observationally determined rates are compared with those calculated on the hypothesis that the modes are stochastically excited by turbulent convection. The observationally determined excitation rate is assumed to be equal to the product of the mode's energy E and its (radian) line width Gamma. We obtain E from the mode's mean square surface velocity with the aid of its velocity eigenfuction. We assume that Gamma measures the mode's energy decay rate, even though quasi-elastic scattering may dominate true absorption. At fixed l, E(Gamma) arises as nu(exp 7) at low nu, reaches a peak at nu approximately equal 3.5 mHz, and then declines as nu(exp 4.4) at higher nu . At fixed nu, E(Gamma) exhibits a slow decline with increasing l. To calculate energy input rates, P(sub alpha), we rely on the mixing-length model of turbulent convection. We find entropy fluctuations to be about an order of magnitude more effective than the Reynolds stress in exciting p-modes . The calculated P(sub alpha) mimic the nu(exp 7) dependence of E(Gamma) at low nu and the nu(exp -4.4) dependence at high nu. The break of 11.4 powers in the nu-dependence of E(Gamma) across its peak is attributed to a combination of (1) the reflection of high-frequency acoustic waves just below the photosphere where the scale height drops precipitously and (2) the absence of energy-bearing eddies with short enough correlation times to excite high-frequency modes. Two parameters associated with the eddy correlation time are required to match the location and shape of the break. The appropriate values of these parameters, while not unnatural, are poorly constrained by theory. The calculated P(sub alpha) can also be made to fit the magnitude of E(Gamma) with a reasonable value for the eddy aspect ratio. Our resutls suggest a possible explanation for the decline of mode energy

  12. Solar p-mode oscillations as a tracer of radial differential rotation

    NASA Technical Reports Server (NTRS)

    Deubner, F.-L.; Ulrich, R. K.; Rhodes, E. J., Jr.

    1979-01-01

    Photoelectric observations of solar p-modes obtained with improved wavenumber and frequency resolution are presented. The observations are compared with model calculations of the p-modes, and the degree of spatial and temporal coherence of the observed wave pattern is investigated. It is found that the p-mode oscillations pervade the visible surface of the sun with a high degree of coherence in space and time, so that the whole complex pattern of standing waves with its nodes and antinodes can be regarded as a fixed pattern corotating with the solar surface layers. The p-modes are introduced as a tracer of solar rotational flow velocities. The equatorial differential rotation is estimated as a function of effective depth on the basis of the theoretical contribution functions for the p-modes recently derived by Ulrich et al. (1978). The results strongly indicate that the angular speed of rotation is not uniform even in the relatively shallow layer extending about 20,000 km below the photosphere.

  13. Low-degree p-mode parameters evolution with solar activity

    NASA Astrophysics Data System (ADS)

    Lochard, J.; Boumier, P.

    We present updated results on the low-degree p-mode parameters changes with solar activity: frequency, spectral width, rotational splittings and spectral asymmetry. A particular attention is devoted to the l=2 splitting asymmetry. Comparaisons of our frequency shifts (derived from the GOLF observations) with predictions of Pr.Dziembowski (based on an extrapolation from intermediate degree modes observations from MDI), are discussed.

  14. Solar seismology. II - The stochastic excitation of the solar p-modes by turbulent convection

    NASA Technical Reports Server (NTRS)

    Goldreich, P.; Keeley, D. A.

    1977-01-01

    We test the hypothesis that the solar p-modes are stabilized by damping due to turbulent viscosity in the convective zone. Starting from the assumption that the modes are stable, we calculate expectation values for the modal energies. We find that the interaction between a p-mode and the turbulent convection is such that the modal energy tends toward equipartition with the kinetic energy of turbulent eddies whose lifetimes are comparable to the modal period. From the calculated values of the modal energies, we compute rms surface velocity amplitudes. Our predicted rms surface velocities range from 0.01 cm/sec for the fundamental radial mode to 0.6 cm/sec for the radial mode whose period is approximately 5 minutes. The predicted surface velocities for the low order p-modes are much smaller than the velocities inferred from recent observations.

  15. Solar seismology. I - The stability of the solar p-modes

    NASA Technical Reports Server (NTRS)

    Goldreich, P.; Keeley, D. A.

    1977-01-01

    The stability of the radial p-modes of the sun is investigated by computing nonadiabatic eigenvalues and eigenfunctions for a solar envelope model which extends from an inner radius of about 0.3 solar radius out to an optical depth of about 0.0003. The calculations take into account in a crude fashion the response of the convective flux to the oscillation. The dynamical effect of turbulence in the convection zone is parametrized in terms of a turbulent shear viscosity. The results show that if damping by turbulent viscosity is neglected, all modes with periods longer than 6 minutes are unstable. The familiar kappa-mechanism, which operates in the H ionization-H(-) opacity region, is the dominant source of driving of the oscillations. Modes with periods shorter than 6 minutes are stabilized by radiative damping in the solar atmosphere. When turbulent dissipation of pulsational energy is included, all modes are predicted to be stable. However, the margin of stability is very small. In view of the large uncertainty that must be assigned to the estimate of turbulent damping, it is concluded that theoretical calculations cannot unequivocally resolve the question of the stability of the solar p-modes.

  16. Energy Loss of Solar p Modes due to the Excitation of Magnetic Sausage Tube Waves: Importance of Coupling the Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Gascoyne, A.; Jain, R.; Hindman, B. W.

    2014-07-01

    We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, Γ, and absorption coefficient, α. The variation of Γ and α as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ≈3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = -z 0).

  17. Mode Conversion of Solar p-Modes in Non-Vertical Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Crouch, A. D.; Cally, P. S.

    2005-03-01

    Sunspots absorb and scatter incident f- and p-modes. Until recently, the responsible absorption mechanism was uncertain. The most promising explanation appears to be mode conversion to slow magnetoacoustic-gravity waves, which carry energy down the magnetic field lines into the interior. In vertical magnetic field, mode conversion can adequately explain the observed f-mode absorption, but is too inefficient to account for the absorption of p-modes. In the first paper of the present series we calculated the efficiency of fast-to-slow magnetoacoustic-gravity wave conversion in uniform non-vertical magnetic fields. We assumed two-dimensional propagation, where the Alfvén waves decouple. In comparison to vertical field, it was found that mode conversion is significantly enhanced in moderately inclined fields, especially at higher frequencies. Using those results, Cally, Crouch, and Braun showed that the resultant p-mode absorption produced by simple sunspot models with non-vertical magnetic fields is ample to explain the observations. In this paper, we further examine mode conversion in non-vertical magnetic fields. In particular, we consider three-dimensional propagation, where the fast and slow magnetoacoustic-gravity waves and the Alfvén waves are coupled. Broadly speaking, the p-mode damping rates are not substantially different to the two-dimensional case. However, we do find that the Alfvén waves can remove similar quantities of energy to the slow MAG waves.

  18. Measurement of Low Signal-To-Noise Ratio Solar p-Modes in Spatially Resolved Helioseismic Data

    NASA Astrophysics Data System (ADS)

    Salabert, D.; Leibacher, J.; Appourchaux, T.; Hill, F.

    2009-05-01

    We present an adaptation of the rotation-corrected, m-averaged spectrum technique designed to observe low signal-to-noise ratio (S/N), low-frequency solar p-modes. The frequency shift of each of the 2l + 1 m spectra of a given (n, l) multiplet is chosen that maximizes the likelihood of the m-averaged spectrum. A high S/N can result from combining individual low S/N, individual-m spectra, none of which would yield a strong enough peak to measure. We apply the technique to Global Oscillation Network Group and Michelson Doppler Imager data and show that it allows us to measure modes with lower frequencies than those obtained with classic peak-fitting analysis of the individual-m spectra. We measure their central frequencies, splittings, asymmetries, lifetimes, and amplitudes. The low frequency, low- and intermediate-angular degrees rendered accessible by this new method correspond to modes that are sensitive to the deep solar interior down to the core (l <= 3) and to the radiative interior (4 <= l <= 35). Moreover, the low-frequency modes have deeper upper turning points, and are thus less sensitive to the turbulence and magnetic fields of the outer layers, as well as uncertainties in the nature of the external boundary condition. As a result of their longer lifetimes (narrower linewidths) at the same S/N the determination of the frequencies of lower frequency modes is more accurate, and the resulting inversions should be more precise.

  19. ON THE PROPAGATION OF p-MODES INTO THE SOLAR CHROMOSPHERE

    SciTech Connect

    De Wijn, A. G.; McIntosh, S. W.; De Pontieu, B.

    2009-09-10

    We employ tomographic observations of a small region of plage to study the propagation of waves from the solar photosphere to the chromosphere using a Fourier phase-difference analysis. Our results show the expected vertical propagation for waves with periods of 3 minutes. Waves with 5 minute periods, i.e., above the acoustic cutoff period, are found to propagate only at the periphery of the plage, and only in the direction in which the field can be reasonably expected to expand. We conclude that field inclination is critically important in the leakage of p-mode oscillations from the photosphere into the chromosphere.

  20. Observations of low-degree p-mode oscillations in 1984. [solar oscillations

    NASA Technical Reports Server (NTRS)

    Henning, Harald M.; Scherrer, Philip H.

    1986-01-01

    Analysis of Stanford differential velocity observations has been extended through the 1984 observing season. Excellent quality observations were obtained in 1984 on 38 days in a 49 day interval from June 20th through August 7th. The power spectrum of this data has been examined and improved frequency determinations have been made for p-modes of degree 2 through 5 and order 5 through 34. Of special interest are the modes of the lower orders, n ranging from 5 to 10, which have not been identified previously.

  1. A Method for the Estimation of p-Mode Parameters from Averaged Solar Oscillation Power Spectra

    NASA Astrophysics Data System (ADS)

    Reiter, J.; Rhodes, E. J., Jr.; Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Larson, T. P.

    2015-04-01

    A new fitting methodology is presented that is equally well suited for the estimation of low-, medium-, and high-degree mode parameters from m-averaged solar oscillation power spectra of widely differing spectral resolution. This method, which we call the “Windowed, MuLTiple-Peak, averaged-spectrum” or WMLTP Method, constructs a theoretical profile by convolving the weighted sum of the profiles of the modes appearing in the fitting box with the power spectrum of the window function of the observing run, using weights from a leakage matrix that takes into account observational and physical effects, such as the distortion of modes by solar latitudinal differential rotation. We demonstrate that the WMLTP Method makes substantial improvements in the inferences of the properties of the solar oscillations in comparison with a previous method, which employed a single profile to represent each spectral peak. We also present an inversion for the internal solar structure, which is based upon 6366 modes that we computed using the WMLTP method on the 66 day 2010 Solar and Heliospheric Observatory/MDI Dynamics Run. To improve both the numerical stability and reliability of the inversion, we developed a new procedure for the identification and correction of outliers in a frequency dataset. We present evidence for a pronounced departure of the sound speed in the outer half of the solar convection zone and in the subsurface shear layer from the radial sound speed profile contained in Model S of Christensen-Dalsgaard and his collaborators that existed in the rising phase of Solar Cycle 24 during mid-2010.

  2. Solar-Cycle Changes in GONG P-Mode Widths and Amplitudes 1995-1998

    NASA Technical Reports Server (NTRS)

    Komm R. W.; Howe, R.; Hill, F.

    1999-01-01

    We search for a solar cycle variation in mode widths and amplitudes derived from 3-month GONG time series. The variation of mode width and amplitude observed in GONG data are the combined effects of fill factor, temporal variation, and measurement uncertainties. The largest variation is caused by the fill factor resulting in modes with increased width and reduced amplitude when fill is lower. We assume that the solar cycle variation is the only other systematic variation beside the temporal window function effect. We correct all currently available data sets for the fill factor and simultaneously derive the solar cycle variation. We find an increase of about 3% on average in mode width from the previous minimum to Oct. 1998 and a decrease of about 7% and 6% in mode amplitude and mode area (width x amplitude). We find no l dependence of the solar-cycle changes. As a function of frequency, these changes show a maximum between 2.7 and 3.3 mHz with about 47% higher than average values for mode width and about 29% and 36% higher ones for mode amplitude and area. We estimate the significance of these rather small changes by a pre-whitening method and find that the results are significant at or above the 99.9% level with mode area showing the highest level of significance and mode width the lowest. The variation in background amplitude is most likely not significant and is consistent with a zero change.

  3. Oscillation frequencies of solar models

    SciTech Connect

    Cox, A.N.; Guzik, J.A.; Kidman, R.B.

    1988-01-01

    Two solar models have been constructed, one with no diffusion of the atomic nuclei, and another including diffusive element separation. The opacity at the bottom of the convection zone was increased 15--20 percent (within its theoretical uncertainty) to obtain a few microhertz agreement with observed p-mode frequencies. Original helium mass fractions were 0.291 and 0.289 for the no-diffusion and diffusion models, respectively. The diffusion model evolved to a surface Y = 0.256 at the solar age, and the original Z value of 0.0200 decreased to 0.0179. Agreement of l = 0 and 2 p-mode frequency separations with those observed is good. The g-mode nonadiabatic solutions do not have equal period spacing until high radial order. The lowest order modes are more visible if they all have the same kinetic energy. High central temperatures, produce over 9 SNUs from the B and 1.5 SNUs from the Be reactions. Models with iron condensed-out below the convection zone, and with WIMPs cooling the central regions to reduce the SNUs, agree less well with p-mode frequency separations. 53 refs., 6 figs., 4 tabs.

  4. Parametrizing the time variation of the `surface term' of stellar p-mode frequencies: application to helioseismic data

    NASA Astrophysics Data System (ADS)

    Howe, R.; Basu, S.; Davies, G. R.; Ball, W. H.; Chaplin, W. J.; Elsworth, Y.; Komm, R.

    2017-02-01

    The solar-cycle variation of acoustic mode frequencies has a frequency dependence related to the inverse mode inertia. The discrepancy between model predictions and measured oscillation frequencies for solar and solar-type stellar acoustic modes includes a significant frequency-dependent term known as the surface term, which is also related to the inverse mode inertia. We parametrize both the surface term and the frequency variations for low-degree solar data from Birmingham Solar-Oscillations Network (BiSON) and medium-degree data from the Global Oscillations Network Group (GONG) using the mode inertia together with cubic and inverse frequency terms. We find that for the central frequency of rotationally split multiplets, the cubic term dominates both the average surface term and the temporal variation, but for the medium-degree case, the inverse term improves the fit to the temporal variation. We also examine the variation of the even-order splitting coefficients for the medium-degree data and find that, as for the central frequency, the latitude-dependent frequency variation, which reflects the changing latitudinal distribution of magnetic activity over the solar cycle, can be described by the combination of a cubic and an inverse function of frequency scaled by inverse mode inertia. The results suggest that this simple parametrization could be used to assess the activity-related frequency variation in solar-like asteroseismic targets.

  5. Dependence of sunspot photospheric waves on the depth of the source of solar p-modes

    NASA Astrophysics Data System (ADS)

    Felipe, T.; Khomenko, E.

    2017-02-01

    Photospheric waves in sunspots moving radially outward at speeds faster than the characteristic wave velocities have been recently detected. It has been suggested that they are the visual pattern of p-modes excited around 5 Mm beneath the sunspot's surface. Using numerical simulations, we performed a parametric study of the waves observed at the photosphere and higher layers that were produced by sources located at different depths beneath the sunspot's surface. The observational measurements are consistent with waves driven between approximately 1 Mm and 5 Mm below the sunspot's surface.

  6. The Solar Core: New Low-l p-Mode Fine-Spacing Results from BiSON

    NASA Astrophysics Data System (ADS)

    Chaplin, W. J.; Elsworth, Y.; Isaak, G. R.; McLeod, C. P.; Miller, B. A.; New, R.

    1997-05-01

    The fine-structure spacing dl(n) = νl,n - νl+2,n-1 for low-degree solar p modes of angular degree l and radial order n is sensitive to conditions in the deep radiative interior of the Sun. Here we present fine-structure spacings derived from the analysis of nearly 5 years of helioseismological data collected between 1991 July and 1996 February by the Birmingham Solar Oscillations Network (BiSON). These data cover 9 <= n <= 28 for d0(n), and 11 <= n <= 27 for d1(n). The measured spacings are much more precise and cover a greater range than earlier measurements from BiSON data (Elsworth et al. 1990a). The predicted fine-structure spacings for a ``standard'' solar model are clearly excluded by the BiSON data (at ~10 σ) models that include helium and heavy-element settling provide a much better match to the observed spacings (see also Elsworth et al. 1995). Since the inclusion of core settling in solar models will tend to increase slightly the predicted neutrino flux, the BiSON fine-structure data appear to reinforce previous conclusions, i.e., an astrophysical solution to the solar neutrino problem seems unlikely. Birmingham Solar Oscillations Network; http://bison.ph.bham.ac.uk.

  7. Solar activity and oscillation frequency splittings

    NASA Technical Reports Server (NTRS)

    Woodard, M. F.; Libbrecht, K. G.

    1993-01-01

    Solar p-mode frequency splittings, parameterized by the coefficients through order N = 12 of a Legendre polynomial expansion of the mode frequencies as a function of m/L, were obtained from an analysis of helioseismology data taken at Big Bear Solar Observatory during the 4 years 1986 and 1988-1990 (approximately solar minimum to maximum). Inversion of the even-index splitting coefficients confirms that there is a significant contribution to the frequency splittings originating near the solar poles. The strength of the polar contribution is anti correlated with the overall level or solar activity in the active latitudes, suggesting a relation to polar faculae. From an analysis of the odd-index splitting coefficients we infer an uppor limit to changes in the solar equatorial near-surface rotatinal velocity of less than 1.9 m/s (3 sigma limit) between solar minimum and maximum.

  8. The Effect of Inhomogeneities on High-Frequency, Low-1 p-Modes: DIFOS Experiment on CORONAS-I

    NASA Technical Reports Server (NTRS)

    Kalkofen, Wolfgang

    1998-01-01

    The investigation of the effects of inhomogeneities of the acoustic modes of the global solar oscillation spectrum has two parts, the first dealing with the prediction of wave fluxes in magnetic flux tubes due to the excitation of longitudinal (i.e. pressure) modes, and the second part, concerning the effects of radiation damping on the p-modes themselves. Part 1 of this work, in collaboration with S.S. Hasan (Indian Institute of Astro- physics, Bangalore), is complete and has resulted in a publication titled Excitation of Longitudinal Modes in Solar Magnetic Flux Tubes, By S.S. Hasan & WK. It is in press in the ASP conference series, containing the proceedings of the Cool Stars conference of 1997, R.A. Donahue and J.A. Bookbinder, editors; publication is expected in 1998. Part 2, in collaboration with Y. Zhugzhda (Izmiran, Moscow) and J. Staude (Sonnenobservatorium Einsteinturm, Potsdam) is in progress and is expected to result in a paper in the forthcoming Boston conference on Helio- and Asteroseismology in June, 1998. A fuller accounting of the work done under the grant will be given when the work started with funding from the grant is complete.

  9. Excitation and Damping of Low-Degree Solar p-Modes during Activity Cycle 23: Analysis of GOLF and VIRGO Sun Photometer Data

    NASA Astrophysics Data System (ADS)

    Jiménez-Reyes, S. J.; García, R. A.; Jiménez, A.; Chaplin, W. J.

    2003-09-01

    We have used observations made by the Global Oscillations at Low Frequency (GOLF) and the Variability of Irradiance and Gravity Oscillations Sun Photometer (VIRGO/SPM) instruments on board the ESA/NASA Solar and Heliospheric Observatory satellite to study variations in the excitation and damping of low angular degree (low-l) solar p-modes on the rising phase of activity cycle 23. Our analysis includes a correction procedure that for the first time allows GOLF data to be ``treated'' as a single homogeneous set, thereby compensating for the change of operational configuration partway through the mission. Over the range 2.5<=ν<=3.5mHz, we uncover an increase in damping and decrease in mode power that is consistent with previous findings. Furthermore, an excellent level of agreement is found between the variations extracted from the GOLF and VIRGO/SPM data. We find no net long-term changes to the modal energy supply rate. However, an analysis of the residuals uncovers the presence of a quasi-periodic signature of period ~1.5 yr (most pronounced for SPM). While it is true that several workers claim to have uncovered similar periodicities in other phenomena related to the near-surface layers of the Sun here, we are at present more inclined to attribute our finding to an artifact of the mode-fitting procedure. We also uncover a significant change in the asymmetry of mode peaks in the GOLF data, as found in previous studies of much longer data sets. These assumed that the dominant contribution to this arose from the switch in operating configuration partway through the mission (which altered the depth in the solar atmosphere sampled by the instrument). However, our preliminary analysis of data collected over the 100 day period beginning 2002 November 19-when the instrument switched back to its original configuration-suggests that this change may have a solar cycle component.

  10. THE ACOUSTIC CUTOFF FREQUENCY OF THE SUN AND THE SOLAR MAGNETIC ACTIVITY CYCLE

    SciTech Connect

    Jimenez, A.; Palle, P. L.; Garcia, R. A.

    2011-12-20

    The acoustic cutoff frequency-the highest frequency for acoustic solar eigenmodes-is an important parameter of the solar atmosphere as it determines the upper boundary of the p-mode resonant cavities. At frequencies beyond this value, acoustic disturbances are no longer trapped but are traveling waves. Interference among them gives rise to higher-frequency peaks-the pseudomodes-in the solar acoustic spectrum. The pseudomodes are shifted slightly in frequency with respect to p-modes, making possible the use of pseudomodes to determine the acoustic cutoff frequency. Using data from the GOLF and VIRGO instruments on board the Solar and Heliospheric Observatory spacecraft, we calculate the acoustic cutoff frequency using the coherence function between both the velocity and intensity sets of data. By using data gathered by these instruments during the entire lifetime of the mission (1996 until the present), a variation in the acoustic cutoff frequency with the solar magnetic activity cycle is found.

  11. Early solar mass loss, element diffusion, and solar oscillation frequencies

    SciTech Connect

    Guzik, J.A.; Cox, A.N.

    1994-07-01

    Swenson and Faulkner, and Boothroyd et al. investigated the possibility that early main-sequence mass loss via a stronger early solar wind could be responsible for the observed solar lithium and beryllium depiction. This depletion requires a total mass loss of {approximately}0.1 M{circle_dot}, nearly independent of the mass loss timescale. We have calculated the evolution and oscillation frequencies of solar models including helium and element diffusion, and such early solar mass loss. We show that extreme mass loss of 1 M{circle_dot} is easily ruled out by the low-degree p-modes that probe the solar center and sense the steeper molecular weight gradient produced by the early phase of more rapid hydrogen burning. The effects on central structure are much smaller for models with an initial mass of 1.1 M{circle_dot} and exponentially-decreasing mass loss irate with e-folding timescale 0.45 Gyr. While such mass loss slightly worsens the agreement between observed and calculated low-degree modes, the observational uncertainties of several tenths of a microhertz weaken this conclusion. Surprisingly, the intermediate-degree modes with much smaller observational uncertainties that probe the convection zone bottom prove to be the key to discriminating between models: The early mass loss phase decreases the total amount of helium and heavier elements diffused from the convection zone, and the extent of the diffusion produced composition gradient just below the convection zone, deteriorating the agreement with observed frequencies for these modes. Thus it appears that oscillations can also rule out this smaller amount of gradual early main-sequence mass loss in the young Sun. The mass loss phase must be confined to substantially under a billion years, probably 0.5 Gyr or less, to simultaneously solve the solar Li/Be problem and avoid discrepancies with solar oscillation frequencies.

  12. Solar oscillation frequency and solar neutrino predictions

    SciTech Connect

    Cox, A.N.

    1990-07-05

    The light and velocity variations of the Sun and solar-like stars are unique among intrinsic variable stars. Unlike all other standard classes, such as Cepheids, B stars, and white dwarfs, the pulsation driving is caused by coupling with the acoustic noise in the upper convection zone. Each global pulsation mode is just another degree of freedom for the turbulent convection, and energy is shared equally between these g{sup {minus}}-modes and the solar oscillation modes. This driving and damping, together with the normal stellar pulsation mechanisms produce extremely low amplitude solar oscillations. Actually, the surface layer radiative damping is strong, and the varying oscillation mode amplitudes manifest the stochastic convection driving and the steady damping. Thus stability calculations for solar-like pulsations are difficult and mostly inconclusive, but calculations of pulsation periods are as straightforward as for all the other classes of intrinsic variable stars. The issue that is important for the Sun is its internal structure, because the mass, radius, and luminosity are extremely well known. Conventionally, we need the pulsation constants for each of millions of modes. Unknown parameters for constructing solar models are the composition and its material pressure, energy, and opacity, as well as the convection mixing length. We treat the nuclear energy and neutrino production formulas as sufficiently well known. The presence of weakly interacting massive particles (WIMPs) orbiting the solar center affects the predicted oscillation frequencies so that they do not agree with observations as well as those for models without WIMPs. 34 refs., 4 figs.

  13. Solar-cycle variations of large frequency separations of acoustic modes: implications for asteroseismology

    NASA Astrophysics Data System (ADS)

    Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; New, R.

    2011-06-01

    We have studied solar-cycle changes in the large frequency separations that can be observed in Birmingham Solar Oscillations Network (BiSON) data. The large frequency separation is often one of the first outputs from asteroseismic studies because it can help constrain stellar properties like mass and radius. We have used three methods for estimating the large separations: use of individual p-mode frequencies, computation of the autocorrelation of frequency-power spectra, and computation of the power spectrum of the power spectrum. The values of the large separations obtained by the different methods are offset from each other and have differing sensitivities to the realization noise. A simple model was used to predict solar-cycle variations in the large separations, indicating that the variations are due to the well-known solar-cycle changes to mode frequency. However, this model is only valid over a restricted frequency range. We discuss the implications of these results for asteroseismology.

  14. Solar emission levels at low radio frequencies

    NASA Technical Reports Server (NTRS)

    Erickson, W. C.

    1990-01-01

    Solar radio emission could seriously interfere with observations made by a low frequency (1 to 10 MHz) array in space. International Sun-Earth Explorer (ISEE-3) radio data were used to determine solar emission level. The results indicate that solar emission should seriously disturb less than ten percent of the data, even during the years of solar maximum. Thus it appears that solar emission should not cause a disastrous loss of data. The information needed to design procedures to excise solar interference from the data produced by any low-frequency array is provided.

  15. The CoRoT B-type binary HD 50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings⋆

    NASA Astrophysics Data System (ADS)

    Degroote, P.; Aerts, C.; Michel, E.; Briquet, M.; Pápics, P. I.; Amado, P.; Mathias, P.; Poretti, E.; Rainer, M.; Lombaert, R.; Hillen, M.; Morel, T.; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Samadi, R.

    2012-06-01

    Context. B-type stars are promising targets for asteroseismic modelling, since their frequency spectrum is relatively simple. Aims: We deduce and summarise observational constraints for the hybrid pulsator, HD 50230, earlier reported to have deviations from a uniform period spacing of its gravity modes. The combination of spectra and a high-quality light curve measured by the CoRoT satellite allow a combined approach to fix the position of HD 50230 in the HR diagram. Methods: To describe the observed pulsations, classical Fourier analysis was combined with short-time Fourier transformations and frequency spacing analysis techniques. Visual spectra were used to constrain the projected rotation rate of the star and the fundamental parameters of the target. In a first approximation, the combined information was used to interpret multiplets and spacings to infer the true surface rotation rate and a rough estimate of the inclination angle. Results: We identify HD 50230 as a spectroscopic binary and characterise the two components. We detect the simultaneous presence of high-order g modes and low-order p and g-modes in the CoRoT light curve, but were unable to link them to line profile variations in the spectroscopic time series. We extract the relevant information from the frequency spectrum, which can be used for seismic modelling, and explore possible interpretations of the pressure mode spectrum. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations made with the ESO telescopes at La Silla Observatory under the ESO Large Programme LP182.D-0356, and on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and on observations obtained with the HERMES

  16. Comparison between simultaneous GOLF and MDI observations in search of low frequency solar oscillations

    NASA Astrophysics Data System (ADS)

    Henney, Carl John

    One of the mission objectives of both the Global Oscillations at Low Frequency (GOLF) and the Michelson Doppler Imager (MDI) instruments aboard the Solar and Heliospheric Observatory (SOHO) is the detection of new low frequency globally coherent solar oscillation modes. After more than two years of nearly continuous observing by both instruments, the clear detection of modes below 1200 μHz has still proven to be elusive. The search for new modes is aided here by combining the high duty cycle of GOLF with the spatial resolution and various data products of MDI. By combining the two data sets, a signal enhancement is anticipated since both instruments provide a low noise data stream and their sources of solar and instrumental noise are expected to be different from each other. Presented here is a comparison between the observed GOLF signal and a selection of spatially masked MDI full-disk signals for a 759 day period from May 25, 1996 through June 22, 1998. The signal-to-background ratio is compared between the various signals for low degree (l <= 3) and low frequency (<2000 μHz) p-modes. It was found that signals from both MDI and GOLF are beneficial for detecting these p-modes. Cross-analysis between GOLF and MDI signals is done to enhance the ability to detect low frequency solar oscillations. Using cross-amplitude and averaged power spectra, an unique list of low degree modes is presented here, along with three new low frequency acoustic mode candidates. Finally, the effects of early main sequence cometary mass accretion with heavy-element diffusion on the solar interior are investigated. For solar models with element diffusion, the addition of mass accretion with a rate suggested by observations of other stars has a negligible effect on the predicted p-mode frequencies for the cases investigated here. The predicted g-mode frequencies exhibit a slight shift of approximately 0.1 μHz with the addition of mass accretion. Compared to previous work, the squared

  17. CMEs and frequency cutoff of solar bursts

    NASA Astrophysics Data System (ADS)

    Stanislavsky, Al.; Konovalenko, Al.; Koval, Ar.; Volvach, Y.; Zarka, P.

    2016-05-01

    Radio observations of solar bursts with high-frequency cutoff by the radio telescope UTR-2 (near Kharkiv, Ukraine) at 8-33 MHz on 17-19 August 2012 are presented. Such cutoff may be attributed to the emergence of the burst sources behind limb of the Sun with respect to an observer on the Earth. The events are strongly associated with solar eruptions occurred in a new active region. Ray tracing simulations show that the CMEs play a constructive role for the behind-limb bursts to be detected in ground-based observations. Likely, due to tunnel-like cavities with low density in CMEs, the radio emission of behind-limb solar bursts can be directed towards the Earth.

  18. On the surface physics affecting solar oscillation frequencies

    NASA Astrophysics Data System (ADS)

    Houdek, G.; Trampedach, R.; Aarslev, M. J.; Christensen-Dalsgaard, J.

    2017-01-01

    Adiabatic oscillation frequencies of stellar models, computed with the standard mixing-length formulation for convection, increasingly deviate with radial order from observations in solar-like stars. Standard solar models overestimate adiabatic frequencies by as much as ˜ 20 μHz. In this Letter, we address the physical processes of turbulent convection that are predominantly responsible for the frequency differences between standard models and observations, also called `surface effects'. We compare measured solar frequencies from the Michelson Doppler Imager instrument on the SOlar and Heliospheric Observatory spacecraft with frequency calculations that include 3D hydrodynamical simulation results in the equilibrium model, non-adiabatic effects, and a consistent treatment of the turbulent pressure in both the equilibrium and stability computations. With the consistent inclusion of the above physics in our model computation, we are able to reproduce the observed solar frequencies to ≲3 μHz without the need of any additional ad hoc functional corrections.

  19. Simultaneous multi-frequency imaging observations of solar microwave bursts

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.; White, S. M.; Schmahl, E. J.

    1989-01-01

    The results of simultaneous two-frequency imaging observations of solar microwave bursts with the Very Large Array are reviewed. Simultaneous 2 and 6 cm observations have been made of bursts which are optically thin at both frequencies, or optically thick at the lower frequency. In the latter case, the source structure may differ at the two frequencies, but the two sources usually seem to be related. However, this is not always true of simultaneous 6 and 20 cm observations. The results have implications for the analysis of nonimaging radio data of solar and stellar flares.

  20. The detection and characterization of high frequency and high wavenumber solar oscillations. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Fernandes, David Neil

    1992-01-01

    Doppler shift measurements of the Na D(sub 1) absorption line have revealed solar oscillations in a new regime of frequency and wavenumber. Oscillations of vertical velocities in the temperature minimum and low chromosphere of the Sun are observed with frequencies ranging up to 9.5 mHz. There is no evidence for chromospheric modes of 3 minute period. This indicates that the chromosphere does not form a good cavity for acoustic waves. The fundamental-modes appear with wavenumbers up to 5.57 M per m (equivalent spherical harmonic degree, 3877). The frequencies lie below the predicted values at wavenumbers above 1 M per m. The values are in agreement with previous measurements that exist for wavenumbers up to 2.67 M per m. Spatial maps of velocity power show that high wavenumber oscillations are suppressed in active regions. The shape of the power depression indicates that wave motion is affected in the layer of atmosphere where the measurement is made. The f-modes are suppressed in the same way as p-modes, indicating that the mechanism for wave suppression affects velocity fluctuations. Mode frequencies are not affected by the magnetic fields by more than 50 micro Hz, the precision of the measurement.

  1. A Technique for Incorporating Large-scale Magnetic Fields Within Stellar Models: Implications for the Variability of the Solar Radius, Luminosity, and Pulsation Frequencies

    NASA Astrophysics Data System (ADS)

    Lydon, T. J.; Sofia, S.

    1994-12-01

    A set of physically consistent approximations are employed to include the effects of magnetic fields within the equations of stellar structure. A series of solar models are then constructed with large-scale (~0.1R_sun), intense (~10(6) gauss) magnetic fields. The results of such models are then compared to measurements of changes in the solar radius (from the Solar Disk Sextant Experiment) and changes in the solar p-mode frequencies in order to determine if such fields are associated with the solar cycle. This work was supported in part by an appointment to the Global Change Distinguished Postdoctoral Fellowships sponsored by the U.S. Department of Energy, Office of Health and Enviromental Research, and administered by the Oak Ridge Institute for Science and Education.

  2. Radio frequency interference affecting type III solar burst observations

    NASA Astrophysics Data System (ADS)

    Anim, N. M.; Hamidi, Z. S.; Abidin, Z. Z.; Monstein, C.; Rohizat, N. S.

    2013-05-01

    The solar burst extinguish from the Sun's corona atmosphere and it dynamical structure of the magnetic field in radio wavelength are studied. Observation of solar radio burst with Compact Astronomical Low cost Low frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) from ETH, Zurich in frequency range of 45 until 870 MHz. Observation done at Pusat Angkasa Negara, Banting, Selangor and successfully detected the solar burst type III on 9th March 2012 from 4:22:00 UT until 4:28:00 UT. The solar burst emission is associated with M6.3 solar flare which occurred at sunspot AR1429 at 03:58UT were observed by NOAA. Frequency ranges chosen as the best ranges for solar monitoring in Malaysia is 150 MHz until 400 MHz. The highest signal amplitude within this frequency ranges is 1.7619 dB at 153.188 MHz (Government Use) have potential to influence the detection of solar radio burst type III within 20 until 400 MHz.

  3. Solar radio astronomy at low frequencies

    NASA Technical Reports Server (NTRS)

    Dulk, George A.

    1990-01-01

    The characteristics of solar radio emissions at decametric to kilometric wavelengths are reviewed. Special attention is given to the radiation of the quiet sun at several metric and decametric wavelengths and to nonthermal radiation from the active sun, including radio bursts of type III (electron beams), type-III bursts from behind the sun, storms of type III bursts, the flare-associated radio bursts, type II bursts (shock waves), and shock-associated bursts. It is pointed out that almost no observations have been made so far of solar radiation between about 20 MHz and about 2 MHz. Below about 2 MHz, dynamic spectra of flux densities of solar burst have been recorded in space and observations were made of the directions of centroids and characteristic sizes of the emitting sources.

  4. Comparative Study of Solar Bursts at Sub-THz Frequencies

    NASA Astrophysics Data System (ADS)

    Fernandes, L. O. T.; Kaufmann, P.; Correia, E.; Marun, A.; Pereyra, P.; Raulin, J.-P.; Valio, A. B. M.

    2016-04-01

    We analyze a large set of 17 solar radio bursts observed at sub-THz (0.2 and 0.4 THz) in 2012-2014 together with the new solar patrol radio telescopes (45 and 90 GHz), operated at El Leoncito, in the Argentinean Andes, allowing the derivation of complete burst spectra in this unexplored range of frequencies. We discuss the uncertainties in sub-THz flux estimates caused by calibration techniques and the corrections for atmospheric transmission. The burst spectra were completed with microwave bursts data obtained by the Radio Solar Telescope Network - RSTN. The events selection was based on GOES soft X-rays burst reported for classes stronger then C. Nearly 50 percent of the bursts exhibited a frequency increasing sub-THz spectral component. The results suggest that the THz component might be always present, with the minimum turn-over frequencies shifting to higher frequencies for larger energies of the electrons producing the emissions.

  5. Solar system radio astronomy at low frequencies

    NASA Technical Reports Server (NTRS)

    Desch, M. D.

    1987-01-01

    The planetary radio-astronomy observations obtained with the two Voyager spacecraft since their launch in 1977 are briefly characterized and illustrated with graphs, diagrams, and sample spectra. Topics addressed include the spacecraft designs and trajectories, the wavelength coverage of the radio instruments, the Io-controlled LF emission of Jupiter, the solar-wind effect on the Saturn kilometric radiation, the Saturn electrostatic discharges, and the use of the clocklike feature of the Uranus emission to measure the planet's rotation period.

  6. Study of p-mode excitation and damping rate variations from IRIS++ observations

    NASA Astrophysics Data System (ADS)

    Salabert, D.; Jiménez-Reyes, S. J.; Tomczyk, S.

    2003-09-01

    11 years of low degree helioseismic data collected by the IRIS++ network (International Research of the Interior of the Sun) have been analyzed. The epoch covered (mid-1989 to end-1999) spans the maximum and the falling phase of solar cycle 22 and the rising phase of the current solar cycle 23. Annual timeseries with an overlap of 6 months are used to study the variations with solar activity of the p-mode frequencies nu n,l, heights Hn,l, and linewidths Gamma n,l, taking into account the effects of the window function. These are used to infer variations in the velocity power and the energy supply rate dot En,l which relate to changes in the excitation and the damping of the modes. We find global changes over the range 2600 <= nu <= 3600 mu Hz of about -26%, 11%, -11% for the heights, the linewidths, and the velocity power respectively, and a constant energy supply to the modes.

  7. A search for p-mode oscillations of Jupiter - Serendipitous observations of nonacoustic thermal wave structure

    NASA Technical Reports Server (NTRS)

    Deming, Drake; Mumma, Michael J.; Espenak, Fred; Jennings, Donald E.; Kostiuk, Theodor; Wiedemann, Gunter

    1989-01-01

    Frequencies for the p-mode oscillations of Jupiter have been determined, and infrared brightness temperature fluctuations are used to search for the modes. Measurements of the infrared intensity of the Jovian disk were obtained in a broad bandwidth using a 20-element linear array. No p-mode oscillations were observed at the 0.07-K level in the 8-13-micron brightness temperature. The results suggest that Jovian p modes are not likely to have observable amplitudes. A prominent nonacoustic wave-like structure in the 8-13-micron brightness temperature is found both at 20 deg N and at the equator.

  8. A search for p-mode oscillations of Jupiter - Serendipitous observations of nonacoustic thermal wave structure

    NASA Astrophysics Data System (ADS)

    Deming, D.; Mumma, M. J.; Espenak, F.; Jennings, D. E.; Kostiuk, T.; Wiedemann, G.; Loewenstein, R.; Piscitelli, J.

    1989-08-01

    Frequencies for the p-mode oscillations of Jupiter have been determined, and infrared brightness temperature fluctuations are used to search for the modes. Measurements of the infrared intensity of the Jovian disk were obtained in a broad bandwidth using a 20-element linear array. No p-mode oscillations were observed at the 0.07-K level in the 8-13-micron brightness temperature. The results suggest that Jovian p modes are not likely to have observable amplitudes. A prominent nonacoustic wave-like structure in the 8-13-micron brightness temperature is found both at 20 deg N and at the equator.

  9. Frequencies and amplitudes of high-degree solar oscillations

    NASA Astrophysics Data System (ADS)

    Kaufman, James Morris

    Measurements of some of the properties of high-degree solar p- and f-mode oscillations are presented. Using high-resolution velocity images from Big Bear Solar Observatory, we have measured mode frequencies, which provide information about the composition and internal structure of the Sun, and mode velocity amplitudes (corrected for the effects of atmospheric seeing), which tell us about the oscillation excitation and damping mechanisms. We present a new and more accurate table of the Sun's acoustic vibration frequencies, nunl, as a function of radial order n and spherical harmonic degree l. These frequencies are averages over azimuthal order m and approximate the normal mode frequencies of a nonrotating spherically symmetric Sun near solar minimum. The frequencies presented here are for solar p- and f-modes with 180 less than or = l less than or = 1920, 0 less than or = n less than or = 8, and 1.7 mHz less than or = nunl less than or = 5.3 mHz. The uncertainties, sigmanl, in the frequencies areas are as low as 3.1 micro-Hz. The theoretically expected f-mode frequencies are given by omega squared = gkh approx. = gl/R, where g is the gravitational acceleration at the surface, kh is the horizontal component of the wave vector, and R is the radius of the Sun. We find that the observed frequencies are significantly less than expected for l greater than 1000, for which we have no explanation. Observations of high-degree oscillations, which have very small spatial features, suffer from the effects of atmospheric image blurring and image motion (or 'seeing'), thereby reducing the amplitudes of their spatial-frequency components. In an attempt to correct the velocity amplitudes for these effects, we simultaneously measured the atmospheric modulation transfer function (MTF) by looking at the effects of seeing on the solar limb. We are able to correct the velocity amplitudes using the MTF out to l approx. = 1200. We find that the frequency of the peak velocity power (as a

  10. Solar observations with a low frequency radio telescope

    NASA Astrophysics Data System (ADS)

    Myserlis, I.; Seiradakis, J.; Dogramatzidis, M.

    2012-01-01

    We have set up a low frequency radio monitoring station for solar bursts at the Observatory of the Aristotle University in Thessaloniki. The station consists of a dual dipole phased array, a radio receiver and a dedicated computer with the necessary software installed. The constructed radio receiver is based on NASA's Radio Jove project. It operates continuously, since July 2010, at 20.1 MHz (close to the long-wavelength ionospheric cut-off of the radio window) with a narrow bandwidth (~5 kHz). The system is properly calibrated, so that the recorded data are expressed in antenna temperature. Despite the high interference level of an urban region like Thessaloniki (strong broadcasting shortwave radio stations, periodic experimental signals, CBs, etc), we have detected several low frequency solar radio bursts and correlated them with solar flares, X-ray events and other low frequency solar observations. The received signal is monitored in ordinary ASCII format and as audio signal, in order to investigate and exclude man-made radio interference. In order to exclude narrow band interference and calculate the spectral indices of the observed events, a second monitoring station, working at 36 MHz, is under construction at the village of Nikiforos near the town of Drama, about 130 km away of Thessaloniki. Finally, we plan to construct a third monitoring station at 58 MHz, in Thessaloniki. This frequency was revealed to be relatively free of interference, after a thorough investigation of the region.

  11. Excitation of electron Langmuir frequency harmonics in the solar atmosphere

    SciTech Connect

    Fomichev, V. V.; Fainshtein, S. M.; Chernov, G. P.

    2013-05-15

    An alternative mechanism for the excitation of electron Langmuir frequency harmonics as a result of the development of explosive instability in a weakly relativistic beam-plasma system in the solar atmosphere is proposed. The efficiency of the new mechanism as compared to the previously discussed ones is analyzed.

  12. Solar S-bursts at Frequencies of 10 - 30 MHz

    NASA Astrophysics Data System (ADS)

    Melnik, V. N.; Konovalenko, A. A.; Rucker, H. O.; Dorovskyy, V. V.; Abranin, E. P.; Lecacheux, A.; Lonskaya, A. S.

    2010-06-01

    Solar S-bursts observed by the radio telescope UTR-2 in the period 2001 - 2002 are studied. The bursts chosen for a detailed analysis occurred in the periods 23 - 26 May 2001, 13 - 16 and 27 - 39 July 2002 during three solar radio storms. More than 800 S-bursts were registered in these days. Properties of S-bursts are studied in the frequency band 10 - 30 MHz. All bursts were always observed against a background of other solar radio activity such as type III and IIIb bursts, type III-like bursts, drift pairs and spikes. Moreover, S-bursts were observed during days when the active region was situated near the central meridian. Characteristic durations of S-bursts were about 0.35 and 0.4 - 0.6 s for the May and July storms, respectively. For the first time, we found that the instantaneous frequency width of S-bursts increased with frequency linearly. The dependence of drift rates on frequency followed the McConnell dependence derived for higher frequencies. We propose a model of S-bursts based on the assumption that these bursts are generated due to the confluence of Langmuir waves with fast magnetosonic waves, whose phase and group velocities are equal.

  13. Short-term changes in solar oscillation frequencies and solar activity

    NASA Technical Reports Server (NTRS)

    Woodard, M. F.; Libbrecht, K. G.; Kuhn, J. R.; Murray, N.

    1991-01-01

    It is shown that the frequencies of solar rho-mode oscillations change significantly over periods as short as one month. These changes correlate significantly with variations in the strength of surface solar activity as measured by the average, over the sun's visible surface, of the magnitude of the line-of-sight magnetic field component from magnetograms. The frequency and mean magnetic variations are found to obey a linear relationship. It is seen that the mean frequency shift at any time depends on the history of solar activity over an interval of, at most, several months prior to the measurement and conclude that the dominant mechanism of the frequency shift is correlated with surface magnetic activity.

  14. No stellar p-mode oscillations in space-based photometry of Procyon.

    PubMed

    Matthews, Jaymie M; Kuschnig, Rainer; Guenther, David B; Walker, Gordon A H; Moffat, Anthony F J; Rucinski, Slavek M; Sasselov, Dimitar; Weiss, Werner W; Kusching, Rainer

    2004-07-01

    Pressure-driven (p-mode) oscillations at the surface of the Sun, resulting from sound waves travelling through the solar interior, are a powerful probe of solar structure, just as seismology can reveal details about the interior of the Earth. Astronomers have hoped to exploit p-mode asteroseismology in Sun-like stars to test detailed models of stellar structure and evolution, but the observations are extremely difficult. The bright star Procyon has been considered one of the best candidates for asteroseismology, on the basis of models and previous reports of p-modes detected in ground-based spectroscopy. Here we present a search for p-modes in 32 days of nearly continuous photometric satellite-based observations of Procyon. If there are p-modes in Procyon, they must have lifetimes less than 2-3 days and/or peak amplitudes <15 parts per million, which defy expectations from the Sun's oscillations and previous theoretical predictions. Target selection for future planned asteroseismology space missions may need to be reconsidered, as will the theory of stellar oscillations.

  15. High-frequency wave normals in the solar wind

    SciTech Connect

    Herbert, F.; Smith, L.D.; Sonett, C.P.

    1984-05-01

    High-frequency (0.01--0.04 Hz) magnetic fluctuations in 506 ten-minute intervals of contemporaneous Explorer 35 and Apollo 12 measurements made in the solar wind near the morning side of the Earth's bow shock show the presence of a large population of disturbances resembling Alfven waves. Each wavefront normal n is systematically aligned (median deviation = 35/sup 0/) with , the associated ten-minute average of the magnetic field. Because of variability in the direction of from one interval to another, the coupled distribution of n is nearly isotropic in solar ecliptic coordinates, in contrast with the results of other studies of waves at much lower frequency indicating outward propagation from the sun. Presumably the high frequency waves discussed here are stirred into isotropy (in solar ecliptic coordinates) by following the low frequency fluctuations. As these waves maintain their alignement of n with despite the great variation of , a strong physical alignment constraint is inferred.

  16. Precision spectroscopy with a frequency-comb-calibrated solar spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.

    2015-06-01

    The measurement of the velocity field of the plasma at the solar surface is a standard diagnostic tool in observational solar physics. Detailed information about the energy transport as well as on the stratification of temperature, pressure and magnetic fields in the solar atmosphere are encoded in Doppler shifts and in the precise shape of the spectral lines. The available instruments deliver data of excellent quality and precision. However, absolute wavelength calibration in solar spectroscopy was so far mostly limited to indirect methods and in general suffers from large systematic uncertainties of the order of 100 m/s. During the course of this thesis, a novel wavelength calibration system based on a laser frequency comb was deployed to the solar Vacuum Tower Telescope (VTT), Tenerife, with the goal of enabling highly accurate solar wavelength measurements at the level of 1 m/s on an absolute scale. The frequency comb was developed in a collaboration between the Kiepenheuer-Institute for Solar Physics, Freiburg, Germany and the Max Planck Institute for Quantum Optics, Garching, Germany. The efforts cumulated in the new prototype instrument LARS (Lars is an Absolute Reference Spectrograph) for solar precision spectroscopy which is in preliminary scientific operation since~2013. The instrument is based on the high-resolution echelle spectrograph of the VTT for which feed optics based on single-mode optical fibres were developed for this project. The setup routinely achieves an absolute calibration accuracy of 60 cm/s and a repeatability of 2.5 cm/s. An unprecedented repeatability of only 0.32 cm/s could be demonstrated with a differential calibration scheme. In combination with the high spectral resolving power of the spectrograph of 7x10^5 and virtually absent internal scattered light, LARS provides a spectral purity and fidelity that previously was the domain of Fourier-transform spectrometers only. The instrument therefore provides unique capabilities for

  17. Spectral Trends of Solar Bursts at Sub-THz Frequencies

    NASA Astrophysics Data System (ADS)

    Fernandes, L. O. T.; Kaufmann, P.; Correia, E.; Giménez de Castro, C. G.; Kudaka, A. S.; Marun, A.; Pereyra, P.; Raulin, J.-P.; Valio, A. B. M.

    2017-01-01

    Previous sub-THz studies were derived from single-event observations. We here analyze for the first time spectral trends for a larger collection of sub-THz bursts. The collection consists of a set of 16 moderate to small impulsive solar radio bursts observed at 0.2 and 0.4 THz by the Solar Submillimeter-wave Telescope (SST) in 2012 - 2014 at El Leoncito, in the Argentinean Andes. The peak burst spectra included data from new solar patrol radio telescopes (45 and 90 GHz), and were completed with microwave data obtained by the Radio Solar Telescope Network, when available. We critically evaluate errors and uncertainties in sub-THz flux estimates caused by calibration techniques and the corrections for atmospheric transmission, and introduce a new method to obtain a uniform flux scale criterion for all events. The sub-THz bursts were searched during reported GOES soft X-ray events of class C or larger, for periods common to SST observations. Seven out of 16 events exhibit spectral maxima in the range 5 - 40 GHz with fluxes decaying at sub-THz frequencies (three of them associated to GOES class X, and four to class M). Nine out of 16 events exhibited the sub-THz spectral component. In five of these events, the sub-THz emission fluxes increased with a separate frequency from that of the microwave spectral component (two classified as X and three as M), and four events have only been detected at sub-THz frequencies (three classified as M and one as C). The results suggest that the THz component might be present throughout, with the minimum turnover frequency increasing as a function of the energy of the emitting electrons. The peculiar nature of many sub-THz burst events requires further investigations of bursts that are examined from SST observations alone to better understand these phenomena.

  18. Estimates of the solar internal angular velocity obtained with the Mt. Wilson 60-foot solar tower

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Woodard, Martin; Tomczyk, Steven; Korzennik, Sylvain

    1987-01-01

    Estimates are obtained of the solar internal angular velocity from measurements of the frequency splittings of p-mode oscillations. A 16-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-foot tower telescope of the Mt. Wilson Observatory is analyzed. Power spectra were computed for all of the zonal, tesseral, and sectoral p-modes from l = 0 to 89 and for all of the sectoral p-modes from l = 90 to 200. A mean power spectrum was calculated for each degree up to 89. The frequency differences of all of the different nonzonal modes were calculated for these mean power spectra.

  19. Seismic Study of The Solar Interior: Inferences from SOI/MDI Observations during Solar Activity

    NASA Technical Reports Server (NTRS)

    Korzennik, Sylvain G.

    2003-01-01

    The principal investigator describes several types of solar research conducted during the reporting period and gives a statement of work to be performed in the following year. Research conducted during the reporting period includes: exhaustive analysis of observational and instrumental effects that might cause systematic errors in the characterization of high-degree p-modes; study of the structure, asphericity and dynamics of the solar interior from p-mode frequencies and frequency splittings; characterizing the solar rotation; Time-Distance inversion; and developing and using a new peak-fitting method for very long MDI time series at low degrees.

  20. Comparison of GONG and MDI solar p-mode background

    NASA Astrophysics Data System (ADS)

    Barban, C.; Hill, F.

    2004-04-01

    Using Severino's model, we estimate the amount of coherent correlated and uncorrelated background and incoherent noise components needed to reproduce the following four helioseismic spectra: V power, I power, V I phase difference and V I coherence, using GONG and MDI data. We confirm that a coherent correlated component of 10-15% of the total background and noise is needed in both V and I and that a larger amount of coherent uncorrelated background is needed for MDI data compared to GONG data to compensate for a smaller incoherent noise.

  1. Depth and latitude dependence of the solar internal angular velocity

    SciTech Connect

    Rhodes, E.J. Jr.; Cacciani, A.; Korzennik, S.; Tomczyk, S.; Ulrich, R.K.; Woodard, M.F. JPL, Pasadena, CA Roma I Universita California Univ., Los Angeles )

    1990-03-01

    One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone. 43 refs.

  2. Depth and latitude dependence of the solar internal angular velocity

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

    1990-01-01

    One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone.

  3. Solar analysis of solar-constant monitoring package (SMM)

    NASA Technical Reports Server (NTRS)

    Hudson, H. S.

    1982-01-01

    The activity cavity radiometer irradiance monitor is supplying the first high precision data on solar total irradiance at the Earth. Thee classes of variability were discovered: large variations of amplitudes up to 0.2%; small high frequency variations in the form of a continuum in the periodogram, extending up to the Nyquist frequency; and sharp spikes at frequencies corresponding to the individual p modes already known from radial velocity measurements. The observed variations (up to 0.3%, on time scales of several days) were identified with sunspot darkness. The data analysis is expected to give information about the solar interior, as well as about the solar input to the terrestrial climate.

  4. The source of solar high-frequency acoustic modes - Theoretical expectations

    NASA Technical Reports Server (NTRS)

    Brown, Timothy M.

    1991-01-01

    The source exciting the solar p-modes is likely to be acoustic noise generated in the top part of the sun's convection zone. If so, then simple arguments suggest that most of the emitted energy may come from rare localized events that are well separated from one another in space and time. This note describes the acoustic emission that would be expected from such events, based on a ray-theory analysis. Most of the acoustic energy is found to emerge very close to the source, so that observations to identify emission events will require high spatial resolution.

  5. Solar-stellar connection: the frequency of maximum oscillation power from solar data

    NASA Astrophysics Data System (ADS)

    Barban, C.; Beuret, M.; Baudin, F.; Belkacem, K.; Goupil, M. J.; Samadi, R.

    2013-06-01

    Stellar oscillations provide powerful tools to derive stellar fundamental parameters such as the mass and radius. These global quantities are derived from scaling relations linking seismic quantities [νmax and Δν to global stellar parameters. These relations use the Sun as a reference. In this work, we used VIRGO and GOLF data to study how the solar frequency at the maximum oscillation power (νmax) varies with time along the solar cycle. We show that these variations imply differences of about 4% in radius and 12% in mass. We showed also that the observational method based on intensity or velocity data has also an impact, implying differences in mass of about 22% and 7% in radius.

  6. Solar Emissions From GHz to Sub-THz Frequencies

    DTIC Science & Technology

    2015-05-21

    long before a very large flare. Similarities between solar flare particle accelerators to laboratory high energy accelerators have been proposed. A...before a very large flare. Possible similarities between solar flare particle accelerators to laboratory high energy accelerators have been proposed. A...various energies prior to the impulsive phase of the large solar flare and coronal mass ejection of 4 November 2003”. Solar Physics, 279, 465-475, 2012

  7. High-frequency acoustic waves are not sufficient to heat the solar chromosphere.

    PubMed

    Fossum, Astrid; Carlsson, Mats

    2005-06-16

    One of the main unanswered questions in solar physics is why the Sun's outer atmosphere is hotter than its surface. Theory predicts abundant production of high-frequency (10-50 mHz) acoustic waves in subsurface layers of the Sun, and such waves are believed by many to constitute the dominant heating mechanism of the chromosphere (the lower part of the outer solar atmosphere) in non-magnetic regions. Such high-frequency waves are difficult to detect because of high-frequency disturbances in Earth's atmosphere (seeing) and other factors. Here we report the detection of high-frequency waves, and we use numerical simulations to show that the acoustic energy flux of these waves is too low, by a factor of at least ten, to balance the radiative losses in the solar chromosphere. Acoustic waves therefore cannot constitute the dominant heating mechanism of the solar chromosphere.

  8. Solar system radio emissions studies with the largest low-frequency radio telescopes

    NASA Astrophysics Data System (ADS)

    Zakharenko, V.; Konovalenko, A.; Litvinenko, G.; Kolyadin, V.; Zarka, P.; Mylostna, K.; Vasylieva, I.; Griessmeier, J.-M.; Sidorchuk, M.; Rucker, H.; Fischer, G.; Cecconi, B.; Coffre, A.; Denis, L.; Shevchenko, V.; Nikolaenko, V.

    2014-04-01

    We describe the trends and tasks in the field of lowfrequency studies of radio emission from the Solar system's objects. The world's largest decameter radio telescopes UTR-2 and URAN have a unique combination of sensitivity and time/frequency resolution parameters, providing the capability of the most detailed studies of various types of solar and planetary emissions.

  9. Ionization frequencies for major thermospheric constituents as a function of solar cycle 21

    NASA Technical Reports Server (NTRS)

    Torr, M. R.; Torr, D. G.; Ong, R. A.; Hinteregger, H. E.

    1979-01-01

    Increases in the solar ultraviolet flux (wavelengths shorter than 1250A) over the past five years of rising solar activity have been larger than anticipated. This increase in UV flux dramatically affects the production of ionization of the various constituents in the thermosphere. Measurements of the solar UV flux by the Atmosphere Explorer satellites are used to determine ionization frequencies for the major thermospheric species for various dates exhibiting notably different levels of solar activity. For the convenience of users of such data, a reduced set of cross-section and flux data is presented for the wavelength range below 1027A, consisting of 37 wavelength intervals

  10. Observations of low-degree P-mode oscillations in 1984

    NASA Technical Reports Server (NTRS)

    Henning, H. M.; Scherrer, P. H.

    1985-01-01

    Analysis of Stanford differential velocity observations has been extended through the 1984 observing season. Excellent quality observations were obtained in 1984 on 38 days in a 49 day interval from June 20th through August 7th. The power spectrum of this data has been examined and improved frequency determinations have been made for p-modes of degree 2 through 5 and order 5 through 34. Of special interest are the modes of the lower orders, n ranging from 5 to 10, which have not been identified previously.

  11. IS THE CURRENT LACK OF SOLAR ACTIVITY ONLY SKIN DEEP?

    SciTech Connect

    Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; Fletcher, S. T.; New, R. E-mail: wjc@bison.ph.bham.ac.uk E-mail: S.Fletcher@shu.ac.uk

    2009-08-01

    The Sun is a variable star whose magnetic activity and total irradiance vary on a timescale of approximately 11 years. The current activity minimum has attracted considerable interest because of its unusual duration and depth. This raises the question: what might be happening beneath the surface where the magnetic activity ultimately originates? The surface activity can be linked to the conditions in the solar interior by the observation and analysis of the frequencies of the Sun's natural seismic modes of oscillation-the p modes. These seismic frequencies respond to changes in activity and are probes of conditions within the Sun. The Birmingham Solar-Oscillations Network (BiSON) has made measurements of p-mode frequencies over the last three solar activity cycles, and so is in a unique position to explore the current unusual and extended solar minimum. We show that the BiSON data reveal significant variations of the p-mode frequencies during the current minimum. This is in marked contrast to the surface activity observations, which show little variation over the same period. The level of the minimum is significantly deeper in the p-mode frequencies than in the surface observations. We observe a quasi-biennial signal in the p-mode frequencies, which has not previously been observed at mid- and low-activity levels. The stark differences in the behavior of the frequencies and the surface activity measures point to activity-related processes occurring in the solar interior, which are yet to reach the surface, where they may be attenuated.

  12. Active power control of solar PV generation for large interconnection frequency regulation and oscillation damping

    DOE PAGES

    Liu, Yong; Zhu, Lin; Zhan, Lingwei; ...

    2015-06-23

    Because of zero greenhouse gas emission and decreased manufacture cost, solar photovoltaic (PV) generation is expected to account for a significant portion of future power grid generation portfolio. Because it is indirectly connected to the power grid via power electronic devices, solar PV generation system is fully decoupled from the power grid, which will influence the interconnected power grid dynamic characteristics as a result. In this study, the impact of solar PV penetration on large interconnected power system frequency response and inter-area oscillation is evaluated, taking the United States Eastern Interconnection (EI) as an example. Furthermore, based on the constructedmore » solar PV electrical control model with additional active power control loops, the potential contributions of solar PV generation to power system frequency regulation and oscillation damping are examined. The advantages of solar PV frequency support over that of wind generator are also discussed. Finally, simulation results demonstrate that solar PV generations can effectively work as ‘actuators’ in alleviating the negative impacts they bring about.« less

  13. Active power control of solar PV generation for large interconnection frequency regulation and oscillation damping

    SciTech Connect

    Liu, Yong; Zhu, Lin; Zhan, Lingwei; Gracia, Jose R.; King, Thomas Jr.; Liu, Yilu

    2015-06-23

    Because of zero greenhouse gas emission and decreased manufacture cost, solar photovoltaic (PV) generation is expected to account for a significant portion of future power grid generation portfolio. Because it is indirectly connected to the power grid via power electronic devices, solar PV generation system is fully decoupled from the power grid, which will influence the interconnected power grid dynamic characteristics as a result. In this study, the impact of solar PV penetration on large interconnected power system frequency response and inter-area oscillation is evaluated, taking the United States Eastern Interconnection (EI) as an example. Furthermore, based on the constructed solar PV electrical control model with additional active power control loops, the potential contributions of solar PV generation to power system frequency regulation and oscillation damping are examined. The advantages of solar PV frequency support over that of wind generator are also discussed. Finally, simulation results demonstrate that solar PV generations can effectively work as ‘actuators’ in alleviating the negative impacts they bring about.

  14. Significant reduction in arc frequency biased solar cells: Observations, diagnostics, and mitigation technique(s)

    NASA Technical Reports Server (NTRS)

    Upschulte, B. L.; Weyl, G. M.; Marinelli, W. J.; Aifer, E.; Hastings, D.; Snyder, D.

    1991-01-01

    A variety of experiments were performed which identify key factors contributing to the arcing of negatively biased high voltage solar cells. These efforts have led to reduction of greater than a factor of 100 in the arc frequency of a single cell following proper remediation procedures. Experiments naturally lead to and focussed on the adhesive/encapsulant that is used to bond the protective cover slip to the solar cell. An image-intensified charge coupled device (CCD) camera system recorded UV emission from arc events which occurred exclusively along the interfacial edge between the cover slip and the solar cell. Microscopic inspection of this interfacial region showed a bead of encapsulant along this entire edge. Elimination of this encapsulant bead reduced the arc frequency by two orders of magnitude. Water contamination was also identified as a key contributor which enhances arcing of the encapsulant bead along the solar cell edge. Spectrally resolved measurements of the observable UV light shows a feature assignable to OH(A-X) electronic emission, which is common for water contaminated discharges. Experiments in which the solar cell temperature was raised to 85 C showed a reduced arcing frequency, suggesting desorption of H2O. Exposing the solar cell to water vapor was shown to increase the arcing frequency. Clean dry gases such as O2, N2, and Ar show no enhancement of the arcing rate. Elimination of the exposed encapsulant eliminates any measurable sensitivity to H2O vapor.

  15. Solar forcing of drought frequency in the Maya lowlands.

    PubMed

    Hodell, D A; Brenner, M; Curtis, J H; Guilderson, T

    2001-05-18

    We analyzed lake-sediment cores from the Yucatan Peninsula, Mexico, to reconstruct the climate history of the region over the past 2600 years. Time series analysis of sediment proxies, which are sensitive to the changing ratio of evaporation to precipitation (oxygen isotopes and gypsum precipitation), reveal a recurrent pattern of drought with a dominant periodicity of 208 years. This cycle is similar to the documented 206-year period in records of cosmogenic nuclide production (carbon-14 and beryllium-10) that is thought to reflect variations in solar activity. We conclude that a significant component of century-scale variability in Yucatan droughts is explained by solar forcing. Furthermore, some of the maxima in the 208-year drought cycle correspond with discontinuities in Maya cultural evolution, suggesting that the Maya were affected by these bicentennial oscillations in precipitation.

  16. Western Wind and Solar Integration Study Phase 3 – Frequency Response and Transient Stability

    SciTech Connect

    Miller, N. W.; Shao, M.; Pajic, S.; D'Aquila, R.

    2014-12-01

    Power system operators and utilities worldwide have concerns about the impact of high-penetration wind and solar generation on electric grid reliability (EirGrid 2011b, Hydro-Quebec 2006, ERCOT 2010). The stability of North American grids under these conditions is a particular concern and possible impediment to reaching future renewable energy goals. Phase 3 of the Western Wind and Solar Integration Study (WWSIS-3) considers a 33% wind and solar annual energy penetration level that results in substantial changes to the characteristics of the bulk power system, including different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior of wind and solar generation. WWSIS-3 evaluates two specific aspects of fundamental frequency system stability: frequency response and transient stability.

  17. Frequency variations of solar radio zebras and their power-law spectra

    NASA Astrophysics Data System (ADS)

    Karlický, M.

    2014-01-01

    Context. During solar flares several types of radio bursts are observed. The fine striped structures of the type IV solar radio bursts are called zebras. Analyzing them provides important information about the plasma parameters of their radio sources. We present a new analysis of zebras. Aims: Power spectra of the frequency variations of zebras are computed to estimate the spectra of the plasma density variations in radio zebra sources. Methods: Frequency variations of zebra lines and the high-frequency boundary of the whole radio burst were determined with and without the frequency fitting. The computed time dependencies of these variations were analyzed with the Fourier method. Results: First, we computed the variation spectrum of the high-frequency boundary of the whole radio burst, which is composed of several zebra patterns. This power spectrum has a power-law form with a power-law index -1.65. Then, we selected three well-defined zebra-lines in three different zebra patterns and computed the spectra of their frequency variations. The power-law indices in these cases are found to be in the interval between -1.61 and -1.75. Finally, assuming that the zebra-line frequency is generated on the upper-hybrid frequency and that the plasma frequency ωpe is much higher than the electron-cyclotron frequency ωce, the Fourier power spectra are interpreted to be those of the electron plasma density in zebra radio sources.

  18. Possible signature of solar oblateness in the Sun's oscillation frequency splittings

    NASA Astrophysics Data System (ADS)

    Woodard, M. F.

    2016-10-01

    Departures from spherical symmetry split the frequencies of the Sun's normal oscillation modes. In addition to the well-studied, dominant splitting of the mode frequencies, due to the first-order advection of internal wave motion, a number of second-order effects of rotation on the frequency splittings, predominantly the solar oblateness, are expected. Whereas the largest rotational frequency splittings have an odd dependence on the azimuthal order, m, of the modes, the second-order effects should have an even dependence. The biggest, and thus far the only well-studied, even-m effect on splittings, is due to the solar-cycle variations in magnetic activity near the Sun's surface, which need to be modeled with some care to bring out the signature of solar oblateness. A crude analysis of the even mode-frequency splittings, obtained from approximately 15 years of SOHO/MDI spherical-harmonic time series, was undertaken. To extract the small even-m splittings of interest from the dominant, solar-cycle effects, which have a strong mode-frequency dependence, the former were assumed to depend only weakly on mode frequency and to have no time dependence. Perhaps the most important finding of the study is that the MDI data are capable of yielding statistically significant estimates of solar oblateness. Indeed the oblateness estimates obtained from the analysis presented here appear to be roughly consistent with both theoretical expectations and with direct measurements of the oblateness. There is also a hint of a pole-equator temperature difference in the seismic measurements, at the level recently suggested by Miesch and Hindman.

  19. Seismic Study of the Solar Interior: Inferences from SOI/MDI Observations During Solar Activity

    NASA Technical Reports Server (NTRS)

    Korzennik, Sylvain G.; Wagner, William J. (Technical Monitor)

    2005-01-01

    Work on the structure, asphericity and dynamics of the solar interior from p-mode frequencies and frequency splittings was carried out primarily in collaboration with Dr. Eff-Darwich (University of La Laguna, Tenerife). This ongoing collaboration produced new results for the inversion of the internal solar rotation rate and further development in inversion methodologies. It also resulted in inferences on the solar stratification. Substantial progress towards the characterization of high-degree p-modes has been achieved. In collaboration with Drs. Rabello-Soares and Schou (Stanford University), we have gained a clear conceptual understanding of the various elements that affect the leakage matrix of the SOI/MDI instrument. This work has precise implications on the properties and the characterization of the HMI instrument being developed for the SDO mission.

  20. Frequency distributions and correlations of solar X-ray flare parameters

    NASA Technical Reports Server (NTRS)

    Crosby, Norma B.; Aschwanden, Markus J.; Dennis, Brian R.

    1993-01-01

    Frequency distributions of flare parameters are determined from over 12,000 solar flares. The flare duration, the peak counting rate, the peak hard X-ray flux, the total energy in electrons, and the peak energy flux in electrons are among the parameters studied. Linear regression fits, as well as the slopes of the frequency distributions, are used to determine the correlations between these parameters. The relationship between the variations of the frequency distributions and the solar activity cycle is also investigated. Theoretical models for the frequency distribution of flare parameters are dependent on the probability of flaring and the temporal evolution of the flare energy build-up. The results of this study are consistent with stochastic flaring and exponential energy build-up. The average build-up time constant is found to be 0.5 times the mean time between flares.

  1. Electromagnetic waves near the proton cyclotron frequency in the solar wind

    NASA Astrophysics Data System (ADS)

    Jian, Lan; Alexander, Robert; Wicks, Robert; Stevens, Michael; Figueroa-Vinas, Adolfo; Russell, Christopher

    2015-04-01

    Strong narrow-band electromagnetic waves around the proton cyclotron frequency have been found sporadically in the solar wind throughout the inner heliosphere. They are nearly-circularly polarized and propagate close to the magnetic field. Electromagnetic waves near the proton cyclotron frequency can be ion cyclotron waves or magnetosonic waves. They can play an important role in modulating the solar wind ion distribution, and contribute to the heating and acceleration of solar wind. Since the waves are left-hand or right-hand polarized in the spacecraft frame with similar characteristics, they are probably due to Doppler shift of a same type of waves, or there could be a mixture of waves with intrinsically different polarizations. Through the assistance of audification, we have studied the long-lasting low frequency wave events in 2005 using high-cadence magnetic field data from the Wind mission. The Solar Wind Experiment team of the Wind mission has provided the temperature anisotropies for core protons, beam protons, and alpha particles, as well as the beam drift for selected cases. We conduct wave dispersion analysis using these ion moments to examine if these waves can be explained by ion cyclotron anisotropy instability or ion beam instability related to the solar wind inhomogeneities.

  2. Sound speed and oscillation frequencies for solar models evolved with Los Alamos ATOMIC opacities

    NASA Astrophysics Data System (ADS)

    Guzik, Joyce A.; Fontes, C. J.; Walczak, P.; Wood, S. R.; Mussack, K.; Farag, E.

    Los Alamos National Laboratory has calculated a new generation of radiative opacities (OPLIB data using the ATOMIC code) for elements with atomic number Z = 1-30 with improved physics input, updated atomic data, and finer temperature grid to replace the Los Alamos LEDCOP opacities released in the year 2000. We calculate the evolution of standard solar models including these new opacities, and compare with models evolved using the Lawrence Livermore National Laboratory OPAL opacities (Iglesias & Rogers 1996). We use the solar abundance mixture of Asplund et al. 2009. The Los Alamos ATOMIC opacities (Colgan et al. 2013a, 2013b, 2015) have steeper opacity derivatives than those of OPAL for temperatures and densities of the solar interior radiative zone. We compare the calculated nonadiabatic solar oscillation frequencies and solar interior sound speed to observed frequencies and helioseismic inferences. The calculated sound-speed profiles are similar for models evolved using either the updated Iben evolution code (see Guzik & Mussack 2010), or the MESA evolution code (Paxton et al. 2015). The LANL ATOMIC opacities partially mitigate the `solar abundance problem'.

  3. Effect of Solar Radiation on Viscoelastic Properties of Bovine Leather: Temperature and Frequency Scans

    NASA Astrophysics Data System (ADS)

    Nalyanya, Kallen Mulilo; Rop, Ronald K.; Onyuka, Arthur S.

    2017-04-01

    This work presents both analytical and experimental results of the effect of unfiltered natural solar radiation on the thermal and dynamic mechanical properties of Boran bovine leather at both pickling and tanning stages of preparation. Samples cut from both pickled and tanned pieces of leather of appropriate dimensions were exposed to unfiltered natural solar radiation for time intervals ranging from 0 h (non-irradiated) to 24 h. The temperature of the dynamic mechanical analyzer was equilibrated at 30°C and increased to 240°C at a heating rate of 5°C \\cdot Min^{-1}, while its oscillation frequency varied from 0.1 Hz to 100 Hz. With the help of thermal analysis (TA) control software which analyzes and generates parameter means/averages at temperature/frequency range, the graphs were created by Microsoft Excel 2013 from the means. The viscoelastic properties showed linear frequency dependence within 0.1 Hz to 30 Hz followed by negligible frequency dependence above 30 Hz. Storage modulus (E') and shear stress (σ ) increased with frequency, while loss modulus (E''), complex viscosity (η ^{*}) and dynamic shear viscosity (η) decreased linearly with frequency. The effect of solar radiation was evident as the properties increased initially from 0 h to 6 h of irradiation followed by a steady decline to a minimum at 18 h before a drastic increase to a maximum at 24 h. Hence, tanning industry can consider the time duration of 24 h for sun-drying of leather to enhance the mechanical properties and hence the quality of the leather. At frequencies higher than 30 Hz, the dynamic mechanical properties are independent of the frequency. The frequency of 30 Hz was observed to be a critical value in the behavior in the mechanical properties of bovine hide.

  4. Frequency dispersion in the admittance of the polycrystalline Cu2S/CdS solar cell

    NASA Astrophysics Data System (ADS)

    Hmurcik, L. V.; Serway, R. A.

    1987-01-01

    The admittance versus frequency for the Cu2S/CdS solar cell was measured. In the dark, the dispersion fits a model of a simple Debye capacitor, with deviation due to grain-boundary scattering at low frequencies. Under illumination, the dispersion becomes a function of surface roughness. Modeled in fractal geometry, the admittance varies as (i x omega) exp m. A second term of this type occurs at high frequencies and at illuminations greater than 0.1 percent AM 1. In this case, the depletion layer extends deep into the CdS due to insufficient charge states at the interface.

  5. Solar and Magnetospheric Influence on High-Frequency Radar Signal Propagation

    NASA Astrophysics Data System (ADS)

    Burrell, A. G.; Yeoman, T. K.; Milan, S. E.; Lester, M.; Lawal, H. A.

    2015-12-01

    The polar ionosphere is a dynamic region that readily responds to changes in solar irradiance, solar wind, the magnetosphere, and the neutral atmosphere. The most recent solar minimum brought to light gaps in the current understanding of the relationship between ionospheric structure and solar irradiance. The Super Dual Auroral Radar Network (SuperDARN) observes the high-latitude ionosphere using coherent scatter High Frequency (HF) radars. SuperDARN has been operational over one and a half solar cycles, and so provides an invaluable dataset for studying long-term ionospheric variability at the northern and southern poles. This study explores the influence of solar and magnetospheric forcing on HF ground-backscatter. Ground-backscatter, the backscatter that returns from a reflection point on the ground rather than from an ionospheric irregularity, provides a measure of the ionospheric density along the propagation path of the radar signal. By exploring the conditions that inhibit or enhance the propagation of ground-backscatter, we improve our understanding of the state of the bottomside ionosphere.

  6. A Time-Frequency Analysis of the Effects of Solar Activities on Tropospheric Thermodynamics

    NASA Technical Reports Server (NTRS)

    Kiang, Richard K.; Kyle, H. Lee; Wharton, Stephen W. (Technical Monitor)

    2001-01-01

    Whether the Sun has significantly influenced the climate during the last century has been under extensive debates for almost two decades. Since the solar irradiance varies very little in a solar cycle, it is puzzling that some geophysical parameters show proportionally large variations which appear to be responding to the solar cycles. For example, variation in low altitude clouds is shown correlated with solar cycle, and the onset of Forbush decrease is shown correlated with the reduction of the vorticity area index. A possible sun-climate connection is that galactic cosmic rays modulated by solar activities influence cloud formation. In this paper, we apply wavelet transform to satellite and surface data to examine this hypothesis. Data analyzed include the time series for solar irradiance, sunspots, UV index, temperature, cloud coverage, and neutron counter measurements. The interactions among the elements in the Earth System under the external and internal forcings give out very complex signals.The periodicity of the forcings or signals could range widely. Since wavelet transforms can analyze multi-scale phenomena that are both localized in frequency and time, it is a very useful technique for detecting, understanding and monitoring climate changes.

  7. Dayside magnetospheric ULF wave frequency modulated by a solar wind dynamic pressure negative impulse

    NASA Astrophysics Data System (ADS)

    Shen, X. C.; Shi, Q. Q.; Zong, Q.-G.; Tian, A. M.; Nowada, M.; Sun, W. J.; Zhao, H. Y.; Hudson, M. K.; Wang, H. Z.; Fu, S. Y.; Pu, Z. Y.

    2017-02-01

    Ultralow frequency (ULF) waves play an important role in the transport of the solar wind energy to the magnetosphere. In this paper, we present a ULF wave event in the dayside magnetosphere which shows a sudden decrease in frequency from 3.1 to 2.3 mHz around 0756 UT on 11 January 2010, when a solar wind dynamic pressure drop (from ˜5 to ˜2 nPa) was observed simultaneously. The wave exits globally. The phase differences between electric and magnetic fields indicate that the compressional mode wave is standing before and after the wave frequency decrease. This result suggests that the ULF wave should be associated with a cavity mode and the frequency decrease might be induced by the change of the cavity size. A theoretical calculation was made to estimate the cavity mode frequency. The calculated wave frequency before/after the negative impulse is 3.8/2.6 mHz, which is consistent with the observations.

  8. Solar Observations at THz Frequencies on Board of a Trans-Antartic Stratospheric Balloon Flight

    NASA Astrophysics Data System (ADS)

    Kaufmann, Pierre; Abrantes, André; Bortolucci, Emilio; Caspi, Amir; Fernandes, Luis Olavo T.; Kropotov, Grigory; Kudaka, Amauri; Laurent, Glenn Thomas; Machado, Nelson; Marcon, Rogério; Marun, Adolfo; Nicolaev, Valery; Hidalgo Ramirez, Ray Fernando; Raulin, Jean-Pierre; Saint-Hilaire, Pascal; Shih, Albert; Silva, Claudemir; Timofeevsky, Alexander

    2016-05-01

    Sub-THz and 30 THz solar burst observations revealed a new spectral component, with fluxes increasing towards THz frequencies, simultaneously with the well known component peaking at microwaves, bringing challenging constraints for interpretation. The THz flare spectra can be completed with measurements made from space. A new system of two photometers was built to observe the Sun at 3 and 7 THz named SOLAR-T. An innovative optical setup allows observations of the full solar disk and detect small burst with sub-second time resolution. The photometers use two Golay cell detectors at the foci of 7.6 cm Cassegrain telescopes. The incoming radiation undergoes low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. The system has been integrated to redundant data acquisition system and Iridium short-burst data services telemetry for monitoring during the flight. SOLAR-T has been flown coupled to U.C. Berkeley solar hard X-ray and gamma-ray imaging spectro-polarimeter GRIPS experiment launched on a NASA CSBF stratospheric balloon from U.S. McMurdo base on January 19, 2016, on a trans-Antarctic flight. The mission ended on January 30. The SOLAR-T on-board computers were recovered from the payload that landed in the Argentina Mountain Range, nearly 2100 km from McMurdo. The SOLAR-T performance was successfully attained, with full space qualification instrumentation. Preliminary results provide the solar disk THz brightness temperatures and indicate a 7 THz burst enhancement time coincident to a sub-THz burst observed by SST during the 28 January GOES C9.6 class soft X-ray burst, the largest occurred during the flight.

  9. Sound speed and oscillation frequencies for a solar model evolved with Los Alamos ATOMIC opacities

    NASA Astrophysics Data System (ADS)

    Guzik, Joyce Ann; Fontes, Christopher; Walczak, Przemyslaw; Wood, Suzannah R.; Mussack, Katie

    2015-08-01

    Los Alamos has calculated a new generation of radiative opacities for elements with atomic number Z=1-30 with improved physics input, updated atomic data, and finer temperature grid to replace the Los Alamos LEDCOP opacities released in the year 2000. We calculate the evolution of a standard solar model including these new opacities, and compare with a model evolved using the Lawrence Livermore National Laboratory OPAL opacities released about 1996. We use the solar abundance mixture of Asplund, Grevesse, Sauval, and Scott (2009), including 2015 updates. The Los Alamos ATOMIC opacities (Colgan et al. 2013a,b) are somewhat higher than those of OPAL for temperatures and densities near the base of the solar convection zone. We compare the calculated nonadiabatic solar oscillation frequencies and solar interior sound speed to observed frequencies and helioseismic inferences. We discuss the potential for increased opacities to partially mitigate the ‘solar abundance problem’.References:J. Colgan, D.P. Kilcrease, N.H. Magee, Jr., G.S.J. Armstrong, J. Abdallah, Jr., M.E. Sherrill, C.J. Fontes, H.L. Zhang and P. Hakel, Eighth International Conference on Atomic and Molecular Data and their Applications: ICAMDATA, Gaithersburg, MD 2012, AIP Conf. Proc. No. 1545, (AIP, New York, 2013a), pp. 17-26.J. Colgan, D.P. Kilcrease, N.H. Magee, Jr, G.S.J. Armstrong, J. Abdallah, Jr., M.E. Sherrill, C.J. Fontes, H.L. Zhang and P. Hakel, High Energy Density Physics 9, 369 (2013b).

  10. High-frequency Plasma Waves Associated with Magnetic Reconnection in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Wang, Y.

    2015-12-01

    Activities of high-frequency plasma waves associated with magnetic reconnection in the solar wind observed by Time Domain Sampler (TDS) experiments on STEREO/WAVES are preliminarily analyzed. The TDS instrument can provide burst mode electric fields data with as long as 16384 sample points at 250 kHz sampling rate. In all 1120 suspected reconnection events, it is found that the most commonly occurred waves are neither ion acoustic waves, electrostatic solitary waves, nor Langmuir/upper hybrid waves, but Bernstein-like waves with harmonics of the electron cyclotron frequency. In addition, to each type of waves, Langmuir/upper hybrid waves reveal the largest occurrence rate in the reconnection region than in the ambient solar wind. These results indicate that Bernstein-like waves and Langmuir/upper hybrid waves might play important roles in the reconnection associated particle heating processes and they might also influence the dissipation of magnetic reconnection.

  11. Comparison of High-Frequency Solar Irradiance: Ground Measured vs. Satellite-Derived

    SciTech Connect

    Lave, Matthew; Weekley, Andrew

    2016-11-21

    High-frequency solar variability is an important to grid integration studies, but ground measurements are scarce. The high resolution irradiance algorithm (HRIA) has the ability to produce 4-sceond resolution global horizontal irradiance (GHI) samples, at locations across North America. However, the HRIA has not been extensively validated. In this work, we evaluate the HRIA against a database of 10 high-frequency ground-based measurements of irradiance. The evaluation focuses on variability-based metrics. This results in a greater understanding of the errors in the HRIA as well as suggestions for improvement to the HRIA.

  12. Two-dimensional multilevel radiative transfer with standard partial frequency redistribution in isolated solar atmospheric structures.

    NASA Astrophysics Data System (ADS)

    Paletou, F.

    1995-10-01

    We have implemented standard partial frequency redistribution (PRD) in a two-dimensional multilevel non-LTE radiative transfer code. The Multilevel Accelerated Lambda Iteration (MALI) method is used. First, a numerical approach for treating standard PRD effects is described, as well as a simple method for treating an optically thick bound-free transition with MALI. Then, the method is validated in mono-dimensional geometry. Finally, preliminary results from two-dimensional radiative modelling of solar prominences are presented.

  13. Measurement of acoustic glitches in solar-type stars from oscillation frequencies observed by Kepler

    SciTech Connect

    Mazumdar, A.; Monteiro, M. J. P. F. G.; Cunha, M. S.; Ballot, J.; Antia, H. M.; Basu, S.; Houdek, G.; Silva Aguirre, V.; Christensen-Dalsgaard, J.; Metcalfe, T. S.; Mathur, S.; García, R. A.; Verner, G. A.; Chaplin, W. J.; Sanderfer, D. T.; Seader, S. E.; Smith, J. C.

    2014-02-10

    For the very best and brightest asteroseismic solar-type targets observed by Kepler, the frequency precision is sufficient to determine the acoustic depths of the surface convective layer and the helium ionization zone. Such sharp features inside the acoustic cavity of the star, which we call acoustic glitches, create small oscillatory deviations from the uniform spacing of frequencies in a sequence of oscillation modes with the same spherical harmonic degree. We use these oscillatory signals to determine the acoustic locations of such features in 19 solar-type stars observed by the Kepler mission. Four independent groups of researchers utilized the oscillation frequencies themselves, the second differences of the frequencies and the ratio of the small and large separation to locate the base of the convection zone and the second helium ionization zone. Despite the significantly different methods of analysis, good agreement was found between the results of these four groups, barring a few cases. These results also agree reasonably well with the locations of these layers in representative models of the stars. These results firmly establish the presence of the oscillatory signals in the asteroseismic data and the viability of several techniques to determine the location of acoustic glitches inside stars.

  14. Possible reasons for the frequency splitting of the harmonics of type II solar radio bursts

    NASA Astrophysics Data System (ADS)

    Eselevich, V. G.; Eselevich, M. V.; Zimovets, I. V.

    2016-01-01

    AIA/SDO data in the 193 Å channel preceding a coronal mass ejection observed at the solar limb on June 13, 2010 are used to simultaneously identify and examine two different shock fronts. The angular size of each front relative to the CME center was about 20°, and their propagation directions differed by ≈25° (≈4° in position angle). The faster front, called the blast shock, advanced the other front, called the piston shock, by R ≈ (0.02-0.03) R⊙ ( R⊙ is the solar radius) and had a maximum initial speed of V B ≈ 850 km/s (with V P ≈ 700 km/s for the piston shock). The appearance and motion of these shocks were accompanied by a Type II radio burst observed at the fundamental frequency F and second harmonic H. Each frequency was split into two close frequencies f 1 and f 2 separated by Δ f = f 2 - f 1 ≪ F, H. It is concluded that the observed frequency splitting Δ f of the F and H components of the Type II burst could result from the simultaneous propagation of piston and blast shocks moving with different speeds in somewhat different directions displaying different coronal-plasma densities.

  15. On Mode Correlation of Solar Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Chang, Heon-Young

    2009-09-01

    In helioseismology it is normally assumed that p-mode oscillations are excited in a statistically independent fashion. Unfortunately, however, this issue is not clearly settled down in that two experiments exist, which apparently look in discrepancy. That is, Appourchaux et al.~(2000) looked at bin-to-bin correlation and found no evidence that the assumption is invalid. On the other hand, Roth (2001) reported that p-mode pairs with nearby frequencies tend to be anti-correlated, possibly by a mode-coupling effect. This work is motivated by an idea that one may test if there exists an excess of anticorrelated power variations of pairs of solar p-modes. We have analyzed a 72-day MDI spherical-harmonic time series to examine temporal variations of p-mode power and their correlation. The power variation is computed by a running-window method after the previous study by Roth (2001), and then distribution function of power correlation between mode pairs is produced. We have confirmed Roth's result that there is an excess of anti-correlated p-mode pairs with nearby frequencies. On the other hand, the amount of excess was somewhat smaller than the previous study. Moreover, the distribution function does not exhibit significant change when we paired modes with non-nearby frequencies, implying that the excess is not due to mode coupling. We conclude that the origin of this excess of anticorrelations may not be a solar physical process, by pointing out the possibility of statistical bias playing the central role in producing the excess.

  16. Analysis of variability of p-mode parameters in 11 years of IRIS data

    NASA Astrophysics Data System (ADS)

    Salabert, D.; Jiménez-Reyes, S. J.; Fossat, E.; Cacciani, A.; Ehgamberdiev, S.; Gelly, B.; Grec, G.; Hoeksema, J. T.; Khalikov, S.; Lazrek, M.; Pallé, P.; Schmider, F. X.; Tomczyk, S.

    2002-03-01

    11 years of IRIS (the low degree helioseismology network) have been analysed for the study of p-modes parameters variability. The duty cycle of the network data has been improved by the partial gap filling method named "repetitive music". This paper discusses the variations of all p-modes parameters along these 11 years.

  17. Statistical Prediction of Solar Particle Event Frequency Based on the Measurements of Recent Solar Cycles for Acute Radiation Risk Analysis

    NASA Technical Reports Server (NTRS)

    Myung-Hee, Y. Kim; Shaowen, Hu; Cucinotta, Francis A.

    2009-01-01

    Large solar particle events (SPEs) present significant acute radiation risks to the crew members during extra-vehicular activities (EVAs) or in lightly shielded space vehicles for space missions beyond the protection of the Earth's magnetic field. Acute radiation sickness (ARS) can impair performance and result in failure of the mission. Improved forecasting capability and/or early-warning systems and proper shielding solutions are required to stay within NASA's short-term dose limits. Exactly how to make use of observations of SPEs for predicting occurrence and size is a great challenge, because SPE occurrences themselves are random in nature even though the expected frequency of SPEs is strongly influenced by the time position within the solar activity cycle. Therefore, we developed a probabilistic model approach, where a cumulative expected occurrence curve of SPEs for a typical solar cycle was formed from a non-homogeneous Poisson process model fitted to a database of proton fluence measurements of SPEs that occurred during the past 5 solar cycles (19 - 23) and those of large SPEs identified from impulsive nitrate enhancements in polar ice. From the fitted model, the expected frequency of SPEs was estimated at any given proton fluence threshold (Phi(sub E)) with energy (E) >30 MeV during a defined space mission period. Corresponding Phi(sub E) (E=30, 60, and 100 MeV) fluence distributions were simulated with a random draw from a gamma distribution, and applied for SPE ARS risk analysis for a specific mission period. It has been found that the accurate prediction of deep-seated organ doses was more precisely predicted at high energies, Phi(sub 100), than at lower energies such as Phi(sub 30) or Phi(sub 60), because of the high penetration depth of high energy protons. Estimates of ARS are then described for 90th and 95th percentile events for several mission lengths and for several likely organ dose-rates. The ability to accurately measure high energy protons

  18. Solar system and related topics study by the methods of the low-frequency radio astronomy

    NASA Astrophysics Data System (ADS)

    Konovalenko, A. A.; Rucker, H. O.; Melnik, V. N.; Falkovich, I. S.; Litvinenko, G. V.; Kolyadin, V. L.; Zakharenko, V. V.; Lecacheux, A.; Zarka, Ph.; Reznik, A. P.

    2010-05-01

    In the present report the possibilities and some results of the high sensitive investigations of the Solar system objects at lowest frequencies have been reviewed. The Sun, Jupiter, Saturn, interplanetary medium, and other objects have been considered. Special attention has been paid to the space weather problem. The stellar-planetary relations have been also investigated, particularly a search of active stars and exo-planets radio emission. During the last years many observations have been performed with the largest decameter arrays UTR-2 (Kharkov, Ukraine) and URAN system (Ukraine) and new receiving equipment. These investigations provided the possibility to get the important information about the fine time-frequency structures of the weak sporadic radio emission. Very good perspectives come into existence in connection to the creation and implementation of the new generation of low-frequency radio telescopes, i.e. LOFAR (the Netherlands), E-LOFAR (European countries), LWA (USA), LSS (France), GURT (Ukraine), etc.

  19. Power spectral density and scaling exponent of high frequency global solar radiation sequences

    NASA Astrophysics Data System (ADS)

    Calif, Rudy; Schmitt, François G.; Huang, Yongxiang

    2013-04-01

    The part of the solar power production from photovlotaïcs systems is constantly increasing in the electric grids. Solar energy converter devices such as photovoltaic cells are very sensitive to instantaneous solar radiation fluctuations. Thus rapid variation of solar radiation due to changes in the local meteorological condition can induce large amplitude fluctuations of the produced electrical power and reduce the overall efficiency of the system. When large amount of photovoltaic electricity is send into a weak or small electricity network such as island network, the electric grid security can be in jeopardy due to these power fluctuations. The integration of this energy in the electrical network remains a major challenge, due to the high variability of solar radiation in time and space. To palliate these difficulties, it is essential to identify the characteristic of these fluctuations in order to anticipate the eventuality of power shortage or power surge. The objective of this study is to present an approach based on Empirical Mode Decomposition (EMD) and Hilbert-Huang Transform (HHT) to highlight the scaling properties of global solar irradiance data G(t). The scale of invariance is detected on this dataset using the Empirical Mode Decomposition in association with arbitrary-order Hilbert spectral analysis, a generalization of (HHT) or Hilbert Spectral Analysis (HSA). The first step is the EMD, consists in decomposing the normalized global solar radiation data G'(t) into several Intrinsic Mode Functions (IMF) Ci(t) without giving an a priori basis. Consequently, the normalized original solar radiation sequence G'(t) can be written as a sum of Ci(t) with a residual rn. From all IMF modes, a joint PDF P(f,A) of locally and instantaneous frequency f and amplitude A, is estimated. To characterize the scaling behavior in amplitude-frequency space, an arbitrary-order Hilbert marginal spectrum is defined to: Iq(f) = 0 P (f,A)A dA (1) with q × 0 In case of scale

  20. Effect of solar activity on the frequency of occurrence of major anomalies in the Arctic. [weather forecasting

    NASA Technical Reports Server (NTRS)

    Bolotinskaya, M. S.

    1978-01-01

    Major air pressure and temperature anomalies in certain arctic regions were studied with a view toward predicting their occurrence. Correlations are sought between the frequency of arctic anomalies and solar activity, or specifically the Wolf number and the index of geomagnetic disturbance. Graphic techniques are used to show that solar activity has a definite influence on the frequency of occurrence of major anomalies of pressure and temperature in the Arctic.

  1. The variations of ionosphere critical frequency of E layer over Chumphon during solar cycle 24

    NASA Astrophysics Data System (ADS)

    Kenpankho, Prasert; Tsugawa, Takuya; Supnithi, Pornchai; Wongcharoen, Poramintra

    The values of the critical frequency of the ionospheric E layer, foE, obtained at Chumphon ionospheric observatory station (geographic 99.37 E, 10.72 N, 3 dip), Thailand, during the year 2007-2012, have been used to investigate the variations of foE over the geomagnetic equatorial region during the solar cycle 24. The investigation, including variations with local time, day, seasons and solar cycle, is in agreement with the observations. A comparison between the observation data and International Reference Ionosphere (IRI) 2012 model has also been made. The IRI 2012 model underestimates foE especially during the period of 7-11 am and after 6 pm for each day and all seasons. Combining with previous investigations, we suggest that underestimation of ionospheric foE by IRI 2012 model is very helpful for the correction of IRI model in an equatorial Asia region.

  2. Computational helioseismology in the frequency domain: acoustic waves in axisymmetric solar models with flows

    NASA Astrophysics Data System (ADS)

    Gizon, Laurent; Barucq, Hélène; Duruflé, Marc; Hanson, Chris S.; Leguèbe, Michael; Birch, Aaron C.; Chabassier, Juliette; Fournier, Damien; Hohage, Thorsten; Papini, Emanuele

    2017-03-01

    Context. Local helioseismology has so far relied on semi-analytical methods to compute the spatial sensitivity of wave travel times to perturbations in the solar interior. These methods are cumbersome and lack flexibility. Aims: Here we propose a convenient framework for numerically solving the forward problem of time-distance helioseismology in the frequency domain. The fundamental quantity to be computed is the cross-covariance of the seismic wavefield. Methods: We choose sources of wave excitation that enable us to relate the cross-covariance of the oscillations to the Green's function in a straightforward manner. We illustrate the method by considering the 3D acoustic wave equation in an axisymmetric reference solar model, ignoring the effects of gravity on the waves. The symmetry of the background model around the rotation axis implies that the Green's function can be written as a sum of longitudinal Fourier modes, leading to a set of independent 2D problems. We use a high-order finite-element method to solve the 2D wave equation in frequency space. The computation is embarrassingly parallel, with each frequency and each azimuthal order solved independently on a computer cluster. Results: We compute travel-time sensitivity kernels in spherical geometry for flows, sound speed, and density perturbations under the first Born approximation. Convergence tests show that travel times can be computed with a numerical precision better than one millisecond, as required by the most precise travel-time measurements. Conclusions: The method presented here is computationally efficient and will be used to interpret travel-time measurements in order to infer, e.g., the large-scale meridional flow in the solar convection zone. It allows the implementation of (full-waveform) iterative inversions, whereby the axisymmetric background model is updated at each iteration.

  3. Transient Stability and Frequency Response of the US Western Interconnection under conditions of High Wind and Solar Generation

    SciTech Connect

    Clark, Kara; Miller, Nicholas W.; Shao, Miaolei; Pajic, Slobodan; D'Aquila, Robert

    2015-04-15

    Adding large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. Our paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrations of wind and solar generation. Moreover, the main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.

  4. Tracing p-mode Waves from the Photosphere to the Corona in Active Regions

    NASA Astrophysics Data System (ADS)

    Zhao, Junwei; Felipe, Tobías; Chen, Ruizhu; Khomenko, Elena

    2016-10-01

    Atmosphere above sunspots is abundant with different types of waves. Among these waves are running penumbral waves in the chromosphere, quasi-periodic oscillations in the lower coronal loops, and recently reported running waves in sunspots’ photosphere, all of which were interpreted as magnetoacoustic waves by some authors. Are these waves in different atmospheric layers related to each other, what is the nature of these waves, and where are the ultimate sources of these waves? Applying a time-distance helioseismic analysis over a suite of multi-wavelength observations above a sunspot, we demonstrate that the helioseismic p-mode waves are able to channel up from the photosphere through the chromosphere and transition region into the corona, and that the magnetoacoustic waves observed in different atmospheric layers are a same wave originating from the photosphere but exhibiting differently under different physical conditions. We also show waves of different frequencies travel along different paths, which can be used to derive the physical properties of the atmosphere above sunspots. Our numerical simulation of traveling of waves from a subphotospheric source qualitatively resembles the observed properties of the waves and offers an interpretation of the shapes of the wavefronts above the photosphere.

  5. Method of frequency dependent correlations: investigating the variability of total solar irradiance

    NASA Astrophysics Data System (ADS)

    Pelt, J.; Käpylä, M. J.; Olspert, N.

    2017-03-01

    Context. This paper contributes to the field of modeling and hindcasting of the total solar irradiance (TSI) based on different proxy data that extend further back in time than the TSI that is measured from satellites. Aims: We introduce a simple method to analyze persistent frequency-dependent correlations (FDCs) between the time series and use these correlations to hindcast missing historical TSI values. We try to avoid arbitrary choices of the free parameters of the model by computing them using an optimization procedure. The method can be regarded as a general tool for pairs of data sets, where correlating and anticorrelating components can be separated into non-overlapping regions in frequency domain. Methods: Our method is based on low-pass and band-pass filtering with a Gaussian transfer function combined with de-trending and computation of envelope curves. Results: We find a major controversy between the historical proxies and satellite-measured targets: a large variance is detected between the low-frequency parts of targets, while the low-frequency proxy behavior of different measurement series is consistent with high precision. We also show that even though the rotational signal is not strongly manifested in the targets and proxies, it becomes clearly visible in FDC spectrum. A significant part of the variability can be explained by a very simple model consisting of two components: the original proxy describing blanketing by sunspots, and the low-pass-filtered curve describing the overall activity level. The models with the full library of the different building blocks can be applied to hindcasting with a high level of confidence, Rc ≈ 0.90. The usefulness of these models is limited by the major target controversy. Conclusions: The application of the new method to solar data allows us to obtain important insights into the different TSI modeling procedures and their capabilities for hindcasting based on the directly observed time intervals.

  6. Solar Radio Burst Data Processing of CALLISTO and Frequency Drift Rate Determination of Solar Radio Burst Detected by CALLISTO Network in Indonesia

    NASA Astrophysics Data System (ADS)

    Batubara, M.; Manik, T.; Suryana, R.; Lathif, M.; Sitompul, P.; Zamzam, M.; Mumtahana, F.

    2017-03-01

    Space Science Center of Indonesian Institute of Aeronautics and Space called LAPAN has installed several solar radio receivers named CALLISTO in various parts of Indonesia. The equipment has made some solar radio observational data which is indicate solar radio burst since its operation. All of the observational data stored in the file format of Flexible Image Transport System (FITS) which is the raw data. Therefore, it is required a such kind of related data processing to produce a data that can be used for further research. In this paper will discuss how the observational data of CALLISTO could be generated included the information of data format, CALLISTO data processing techniques used in these activities as well as some of the data processing based on data indicating solar radio bursts. As the results, a map of solar radio spectrum as spectrograph profiles and some determinations of frequency drift base on the data will also be discussed in this paper.

  7. High Frequency Plasma Waves Associated With Solar Wind Reconnection Exhausts: WIND/WAVES Observations

    NASA Astrophysics Data System (ADS)

    Huttunen, K. E.; Bale, S. D.; Phan, T. D.; Davis, M.; Gosling, J. T.

    2006-12-01

    Observations of strong plasma wave activity near reconnection X-line regions in THE laboratory and in the Earth's magnetosphere have suggested that plasma waves may play AN important role in the reconnection process by providing anomalous resistivity through wave-particle interactions and by accelerating electrons. Recent observations of quasi-steady magnetic reconnection in the solar wind introduces an important new environment to study the role of plasma waves in a collisionless plasma associated with the reconnection process. We have used observations by the WIND spacecraft to study high frequency plasma waves associated with 28 solar wind reconnection exhausts. The TNR (Thermal Noise Receiver) experiment included in the WAVES instrument on WIND measures electric spectral density from 4 to 256 kHz and the TDS (Time Domain Sampler) experiment also included in WAVES samples electric field waveforms at rates up to 120,000 samples/s. A large fraction (79%) of the investigated events showed significant enhancements in the wave power around ~ 4 kHz, while only about one third (39%) of the exhausts were associated with intensifications around THE local electron plasma frequency (few tens of kHz). TDS waveform samples revealed three different wave modes: electron solitary waves, ion acoustic waves and Langmuir waves. The intense plasma waves were most frequently observed close to the X-line and near the exhaust boundaries, although wave emissions were commonly observed elsewhere within the exhausts as well

  8. FREQUENCY DEPENDENCE OF POLARIZATION OF ZEBRA PATTERN IN TYPE-IV SOLAR RADIO BURSTS

    SciTech Connect

    Kaneda, Kazutaka; Misawa, H.; Tsuchiya, F.; Obara, T.; Iwai, K.

    2015-08-01

    We investigated the polarization characteristics of a zebra pattern (ZP) in a type-IV solar radio burst observed with AMATERAS on 2011 June 21 for the purpose of evaluating the generation processes of ZPs. Analyzing highly resolved spectral and polarization data revealed the frequency dependence of the degree of circular polarization and the delay between two polarized components for the first time. The degree of circular polarization was 50%–70% right-handed and it varied little as a function of frequency. Cross-correlation analysis determined that the left-handed circularly polarized component was delayed by 50–70 ms relative to the right-handed component over the entire frequency range of the ZP and this delay increased with the frequency. We examined the obtained polarization characteristics by using pre-existing ZP models and concluded that the ZP was generated by the double-plasma-resonance process. Our results suggest that the ZP emission was originally generated in a completely polarized state in the O-mode and was partly converted into the X-mode near the source. Subsequently, the difference between the group velocities of the O-mode and X-mode caused the temporal delay.

  9. Metal-dielectric frequency-selective surface for high performance solar window coatings

    NASA Astrophysics Data System (ADS)

    Toor, Fatima; Guneratne, Ananda C.; Temchenko, Marina

    2016-03-01

    We demonstrate a solar control window film consisting of metallic nanoantennas designed to reflect infrared (IR) light while allowing visible light to pass through. The film consists of a capacitive frequency-selective surface (CFSS) which acts as a band-stop filter, reflecting only light at target wavelengths. The designed CFSS when installed on windows will lower air conditioning costs by reflecting undesired wavelengths of light and thus reduce the amount of heat that enters a building. State-of-the-art commercial solar control films consist of a multilayer stack which is costly ( 13/m2 to 40/m2) to manufacture and absorbs IR radiation, causing delamination or glass breakage when attached to windows. Our solar control film consists of a nanostructured metallic layer on a polyethylene terephthalate (PET) substrate that reflects IR radiation instead of absorbing it, solving the delamination problem. The CFSS is also easy to manufacture with roll-to-roll nanoimprint lithography at a cost of <$12/m2. We design the CFSS using the COMSOL Wave Optics module to solve for electromagnetic wave propagation in optical media via the finite element method. The simulation domain is reduced to a single unit cell with periodic boundary conditions to account for the symmetries of the planar, periodic CFSS. The design is optimized using parametric sweeps around the various geometric components of the metallic nanoantenna. Our design achieves peak reflection of 80% at 1000 nm and has a broadband IR response that will allow for optimum solar control without significantly affecting the transmission of visible light.

  10. A search for p-mode pulsations in white dwarf stars using the Berkeley Visible Imaging Tube detector

    NASA Astrophysics Data System (ADS)

    Kilkenny, D.; Welsh, B. Y.; Koen, C.; Gulbis, A. A. S.; Kotze, M. M.

    2014-01-01

    We present high-speed photometry (resolution 0.1 s) obtained during the commissioning of the Berkely Visible Imaging Tube system on the Southern African Large Telescope (SALT). The observations were an attempt to search for very rapid p-mode oscillations in white dwarf stars and included three DA stars known to be g-mode pulsators (ZZ Cet, HK Cet and AF Pic), one other DA star (WD 1056-384) not known to be variable and one AM Cvn star (HP Lib). No evidence was found for any variations greater than about 1 mmag in amplitude (˜0.1 per cent) at frequencies in excess of 60 mHz (periods <17 s) in any of the target stars, though several previously known g-mode frequencies were recovered.

  11. Oscillation frequencies for 35 Kepler solar-type planet-hosting stars using Bayesian techniques and machine learning

    NASA Astrophysics Data System (ADS)

    Davies, G. R.; Silva Aguirre, V.; Bedding, T. R.; Handberg, R.; Lund, M. N.; Chaplin, W. J.; Huber, D.; White, T. R.; Benomar, O.; Hekker, S.; Basu, S.; Campante, T. L.; Christensen-Dalsgaard, J.; Elsworth, Y.; Karoff, C.; Kjeldsen, H.; Lundkvist, M. S.; Metcalfe, T. S.; Stello, D.

    2016-02-01

    Kepler has revolutionized our understanding of both exoplanets and their host stars. Asteroseismology is a valuable tool in the characterization of stars and Kepler is an excellent observing facility to perform asteroseismology. Here we select a sample of 35 Kepler solar-type stars which host transiting exoplanets (or planet candidates) with detected solar-like oscillations. Using available Kepler short cadence data up to Quarter 16 we create power spectra optimized for asteroseismology of solar-type stars. We identify modes of oscillation and estimate mode frequencies by `peak bagging' using a Bayesian Markov Chain Monte Carlo framework. In addition, we expand the methodology of quality assurance using a Bayesian unsupervised machine learning approach. We report the measured frequencies of the modes of oscillation for all 35 stars and frequency ratios commonly used in detailed asteroseismic modelling. Due to the high correlations associated with frequency ratios we report the covariance matrix of all frequencies measured and frequency ratios calculated. These frequencies, frequency ratios, and covariance matrices can be used to obtain tight constraint on the fundamental parameters of these planet-hosting stars.

  12. Beam-plasma instability in the presence of low-frequency turbulence. [during type 3 solar emission

    NASA Technical Reports Server (NTRS)

    Goldman, M. V.; Dubois, D. F.

    1982-01-01

    General equations are derived for a linear beam-plasma instability in the presence of low-frequency turbulence. Within a 'quasi-linear' statistical approximation, these equations contain Langmuir wave scattering, diffusion, resonant and nonresonant anomalous absorption, and a 'plasma laser' effect. It is proposed that naturally occurring density irregularities in the solar wind may stabilize the beam-unstable Langmuir waves which occur during type III solar emissions.

  13. A statistical study on the occurrence of discrete frequencies in the high velocity solar wind and in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Di Matteo, Simone; Villante, Umberto

    2016-04-01

    The possible occurrence of oscillations at discrete frequencies in the solar wind and their possible correspondence with magnetospheric field oscillations represent an interesting aspect of the solar wind/magnetopheric research. We analyze a large set of high velocity streams following interplanetary shocks in order to ascertain the possible occurrence of preferential sets of discrete frequencies in the oscillations of the solar wind pressure in such structures. We evaluate, for each event, the power spectrum of the dynamic pressure by means of two methods (Welch and multitaper windowing) and accept the common spectral peaks that also pass a harmonic F-test at the 95% confidence level. We compare these frequencies with those detected at geosynchronous orbit in the magnetospheric field components soon after the manifestation of the corresponding Sudden Impulses.

  14. Solar burst with millimetre-wave emission at high frequency only

    NASA Technical Reports Server (NTRS)

    Kaufmann, P.; Correia, E.; Costa, J. E. R.; Vaz, A. M. Z.; Dennis, B. R.

    1985-01-01

    The first high sensitivity and high time-resolution observations of a solar burst taken simultaneously at 90 GHz and at 30 GHz are presented. These identify a unique impulsive burst on May 21, 1984 with fast pulsed emission that was considerably more intense at 90 GHz than at lower frequencies. Hard X-ray time structures at energies above 25 keV were almost identical to the 90 GHz structures to better than 1 s. The structure of the onset of the major 90 GHz burst coincided with the hard X-ray structure to within 128 ms. All 90 GHz major time structures consisted of trains of multiple subsecond pulses with rise times as short as 0.03 s and amplitudes that were large compared with the mean flux. When detectable, the 30 GHz subsecond pulses had smaller relative amplitude and were in phase with the corresponding 90 GHz pulses.

  15. Transverse low frequency wave in a two fluid solar wind. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Solodyna, G. V.

    1973-01-01

    Investigation is made of the properties of low frequency transverse waves in a two-fluid solar wind having a radial magnetic field and radial streaming velocity. In order to examine what effects this streaming medium has on the waves, linearly polarized waves are decomposed into left and right circularly polarized waves. Computation is made of analytic expressions valid to first order for the radial amplitude and phase dependence of these constituent waves. It is shown that after travelling a given distance r, these waves have different amplitudes and phases. The former result causes their superposition to become elliptical rather than linear. The latter causes the axis of the ellipse of polarization to rotate through a well-defined angle. Analytic expressions are obtained for the eccentricity of the ellipse and for the angle of rotation. In analogy with regular Faraday rotation, in which the plane of polarization of a linear polarized wave rotates, the effect is denoted as generalized Faraday rotation.

  16. Two-frequency imaging of microwave impulsive flares near the solar limb

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.; Bastian, T. S.; Kane, S. R.

    1986-01-01

    VLA observations of two impulsive microwave and hard X-ray flares close to the solar limb on November 21 and 22, 1981 are presently interpreted in terms of an inhomogeneous flare volume, with the magnetic field strength and orientation varying with position both transverse to, and along, the line-of-sight. The 15 GHz radiation of the flares on both days may be due to electrons of E = 300 keV in weak nonthermal tail; the absence of 4.9 GHz radiation from these sources is attributed to absorption along the ray path from the flare to the earth, on the basis of the fact that thermal bremsstrahlung and gyrosynchrotron radiation mechanisms generate more low than high frequency radiation.

  17. LOW-FREQUENCY OBSERVATIONS OF TRANSIENT QUASI-PERIODIC RADIO EMISSION FROM THE SOLAR ATMOSPHERE

    SciTech Connect

    Sasikumar Raja, K.; Ramesh, R.

    2013-09-20

    We report low-frequency observations of quasi-periodic, circularly polarized, harmonic type III radio bursts whose associated sunspot active regions were located close to the solar limb. The measured periodicity of the bursts at 80 MHz was ≈5.2 s, and their average degree of circular polarization (dcp) was ≈0.12. We calculated the associated magnetic field B (1) using the empirical relationship between the dcp and B for the harmonic type III emission, and (2) from the observed quasi-periodicity of the bursts. Both the methods result in B ≈ 4.2 G at the location of the 80 MHz plasma level (radial distance r ≈ 1.3 R{sub ☉}) in the active region corona.

  18. Oblique Bernstein Mode Generation Near the Upper-hybrid Frequency in Solar Pre-flare Plasmas

    NASA Astrophysics Data System (ADS)

    Kryshtal, A.; Fedun, V.; Gerasimenko, S.; Voitsekhovska, A.

    2015-11-01

    We study analytically the generation process of the first harmonics of the pure electron weakly oblique Bernstein modes. This mode can appear as a result of the rise and development of a corresponding instability in a solar active region. We assume that this wave mode is modified by the influence of pair Coulomb collisions and a weak large-scale sub-Dreicer electric field in the pre-flare chromosphere near the footpoints of a flare loop. To describe the pre-flare plasma we used the model of the solar atmosphere developed by Fontenla, Avrett, and Loeser ( Astrophys. J. 406, 319, 1993). We show that the generated first harmonic is close to the upper-hybrid frequency. This generation process begins at the very low threshold values of the sub-Dreicer electric field and well before the beginning of the preheating phase of a flare. We investigate the necessary conditions for the existence of non-damped first harmonics of oblique Bernstein waves with small amplitudes in the flare area.

  19. Multi-scale harmonic model for solar and climate cyclical variation throughout the Holocene based on Jupiter-Saturn tidal frequencies plus the 11-year solar dynamo cycle

    NASA Astrophysics Data System (ADS)

    Scafetta, Nicola

    2012-05-01

    The Schwabe frequency band of the Zurich sunspot record since 1749 is found to be made of three major cycles with periods of about 9.98, 10.9 and 11.86 years. The side frequencies appear to be closely related to the spring tidal period of Jupiter and Saturn (range between 9.5 and 10.5 years, and median 9.93 years) and to the tidal sidereal period of Jupiter (about 11.86 years). The central cycle may be associated to a quasi-11-year solar dynamo cycle that appears to be approximately synchronized to the average of the two planetary frequencies. A simplified harmonic constituent model based on the above two planetary tidal frequencies and on the exact dates of Jupiter and Saturn planetary tidal phases, plus a theoretically deduced 10.87-year central cycle reveals complex quasi-periodic interference/beat patterns. The major beat periods occur at about 115, 61 and 130 years, plus a quasi-millennial large beat cycle around 983 years. We show that equivalent synchronized cycles are found in cosmogenic records used to reconstruct solar activity and in proxy climate records throughout the Holocene (last 12,000 years) up to now. The quasi-secular beat oscillations hindcast reasonably well the known prolonged periods of low solar activity during the last millennium such as the Oort, Wolf, Spörer, Maunder and Dalton minima, as well as the 17 115-year long oscillations found in a detailed temperature reconstruction of the Northern Hemisphere covering the last 2000 years. The millennial three-frequency beat cycle hindcasts equivalent solar and climate cycles for 12,000 years. Finally, the harmonic model herein proposed reconstructs the prolonged solar minima that occurred during 1900-1920 and 1960-1980 and the secular solar maxima around 1870-1890, 1940-1950 and 1995-2005 and a secular upward trending during the 20th century: this modulated trending agrees well with some solar proxy model, with the ACRIM TSI satellite composite and with the global surface temperature

  20. Harmonic model for solar and climate cyclical variation throughout the Holocene based on Jupiter-Saturn tidal frequencies plus the 11-year solar dynamo cycle

    NASA Astrophysics Data System (ADS)

    Scafetta, N.

    2012-12-01

    We show that the Schwabe frequency band of the Zurich sunspot record since 1749 is made of three major cycles that are closely related to the spring tidal period of Jupiter and Saturn (~9.93 year), to the tidal sidereal period of Jupiter (about 11.86 years) and to a central cycle that may be associated to a quasi-11-year solar dynamo cycle. The central harmonic is approximately synchronized to the average of the two planetary frequencies. A harmonic model based on the above two planetary tidal frequencies and on the exact dates of Jupiter and Saturn planetary tidal phases, plus a theoretically deduced 10.87-year central cycle reveals major beat periods occurring at about 115, 61 and 130 years, plus a quasi-millennial large beat cycle around 983 years. Equivalent synchronized cycles are found in cosmogenic solar proxy records used to reconstruct solar activity and in proxy climate records throughout the Holocene (last 12,000 years) up to now. The quasi-secular beat oscillations hindcast reasonably well the known prolonged periods of low solar activity during the last millennium such as the Oort, Wolf, Sporer, Maunder and Dalton minima, as well as the 17 115-year long oscillations found in a detailed temperature reconstruction of the Northern Hemisphere covering the last 2000 years. The millennial three-frequency beat cycle hindcasts equivalent solar and climate cycles for 12,000 years. Finally, the harmonic model herein proposed reconstructs the prolonged solar minima around 1900-1920 and 1960-1980, the secular solar maxima around 1870-1890, 1940-1950 and 1995-2005, and a secular upward trending during the 20th century. The latter modulated trending agrees well with some solar proxy model, with the ACRIM TSI satellite composite and with the global surface temperature modulation since 1850. The model forecasts a new prolonged solar minimum during 2020-2045, which is produced by the minima of both the 61 and 115-year reconstructed cycles. Finally, the model predicts

  1. Registration of ionospheric effect of 20 March 2015 solar eclipse from GPS data in single-frequency mode

    NASA Astrophysics Data System (ADS)

    Kolmogorov, Andrey; Ivanov, Vsevolod; Gorbachev, Oleg

    2015-12-01

    This article is devoted to the influence of solar eclipse of 20 March 2015 on the total electron content (TEC) of the ionosphere with using data from satellite navigation system GPS. In addition to considering TEC variations, one of the main aims was to show the possibility of using the data of the single-frequency receivers for the diagnostics of the ionosphere. Data from the single-frequency receivers were compared with dual-frequency receivers GPS. As a result, the possibility of using of the low-cost and mobile single-frequency devices for diagnostics of the ionosphere has been demonstrated. It should be noted that the data from the single-frequency receivers, as expected, showed a more noisy result, compared with the phase measurement on two-frequencies. However, after filtering high frequency harmonics result was very similar.

  2. Observations of intermediate degree solar oscillations - 1989 April-June

    NASA Technical Reports Server (NTRS)

    Bachmann, Kurt T.; Schou, Jesper; Brown, Timothy M.

    1993-01-01

    Frequencies, splittings, and line widths from 85 d of full disk Doppler observations of solar p-modes taken between April 4 and June 30, 1989 are presented. Comparison of the present mode parameters with published Big Bear Solar Observatory (BBSO) results yields good agreement in general and is thus a confirmation of their work using an independent instrument and set of analysis routines. Average differences in p-mode frequencies measured by the two experiments in spring-summer 1989 are explained as a result of differences in the exact periods of data collection during a time of rapidly changing solar activity. It is shown that the present a(1) splitting coefficients for p-modes with nu/L less than 45 micro-Hz suffer from a significant systematic error. Evidence is presented to the effect that a detector distortion or alignment problem, not a problem with the power spectra analysis, is the most likely explanation of this a(1) anomaly.

  3. Ion Acoustic Wave Frequencies and Onset Times During Type 3 Solar Radio Bursts

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Robinson, P. A.

    1995-01-01

    Conflicting interpretations exist for the low-frequency ion acoustic (S) waves often observed by ISEE 3 in association with intense Langmuir (L) waves in the source regions of type III solar radio bursts near 1 AU. Two indirect lines of observational evidence, as well as plasma theory, suggest they are produced by the electrostatic (ES) decay L yields L(PRIME) + S. However, contrary to theoretical predictions, an existing analysis of the wave frequencies instead favors the electromagnetic (EM) decays L yields T + S, where T denotes an EM wave near the plasma frequency. This conflict is addressed here by comparing the observed wave frequencies and onset times with theoretical predictions for the ES and EM decays, calculated using the time-variable electron beam and magnetic field orientation data, rather than the nominal values used previously. Field orientation effects and beam speed variations are shown analytically to produce factor-of-three effects, greater than the difference in wave frequencies predicted for the ES and EM decays; effects of similar magnitude occur in the events analyzed here. The S-wave signals are extracted by hand from a sawtooth noise background, greatly improving the association between S waves and intense L waves. Very good agreement exists between the time-varying predictions for the ES decay and the frequencies of most (but not all) wave bursts. The waves occur only after the ES decay becomes kinematically allowed, which is consistent with the ES decay proceeding and producing most of the observed signals. Good agreement exists between the EM decay's predictions and a significant fraction of the S-wave observations while the EM decay is kinematically allowed. The wave data are not consistent, however, with the EM decay being the dominant nonlinear process. Often the observed waves are sufficiently broadband to overlap simultaneously the frequency ranges predicted for the ES and EM decays. Coupling the dominance of the ES decay with this

  4. Narrow band wave emissions and noise around the plasma frequency in the solar wind

    NASA Astrophysics Data System (ADS)

    Chugunov, Yu. V.; Hayosh, M.; Fiala, V.; Soucek, J.; Santolik, O.; Pickett, J.

    2007-08-01

    The wave data obtained with a wide band instrument were recently used for interpretation of both quasi-thermal noise spectra and narrow band signals observed in the near vicinity of the local plasma frequency on CLUSTER II spacecraft in the solar wind, well upstream of the Earth's bow shock [1, 2] This approach is planned to continue with the large Cluster database and will be of use for other space missions such as Stereo and Solar Orbiter. If available, multi-component and/or multi-point measurements are expected to provide even greater insight in the generation of radio waves in the heliosphere in this frequency range. Our approach is based on a novel study of performance of receiving antennas in resonance regions in a streaming plasma. As far as noise spectra is concerned two distinctive features appear: a cutoff shifted down below the plasma frequency by a factor proportional to the ratio of stream velocity to the electron thermal velocity squared. The spectral maximum depends on the orientation of the antenna axis with respect to the stream velocity; it is shifted above the plasma frequency according to the antenna orientation, which is changing with the spacecraft spin. When the time resolution of the instrument is sufficient, it is possible to follow these changes. The overall form of the spectrum depends on the plasma distribution function, but even with a simplified model of two electron populations with largely different temperatures the estimates of the drift velocity and/or the temperature of the hot component can be obtained. In the case of a quasi-harmonic wave (narrow band signal) incident on the antenna, it is the antenna's effective length that allows for conversion of the open circuit voltage induced on its terminals to the electric field of the incoming wave. We show that this effective length grows by more than an order of magnitude under resonance conditions. This was already confirmed for waves propagating close to the lower oblique resonance

  5. HIGH DYNAMIC RANGE OBSERVATIONS OF SOLAR CORONAL TRANSIENTS AT LOW RADIO FREQUENCIES WITH A SPECTRO-CORRELATOR

    SciTech Connect

    Hariharan, K.; Ramesh, R.; Kathiravan, C.; Rajalingam, M.; Abhilash, H. N.

    2016-02-15

    A new antenna system with a digital spectro-correlator that provides high temporal, spectral, and amplitude resolutions has been commissioned at the Gauribidanur Observatory near Bangalore in India. Presently, it is used for observations of the solar coronal transients in the scarcely explored frequency range ≈30–15 MHz. The details of the antenna system, the associated receiver setup, and the initial observational results are reported. Some of the observed transients exhibited quasi-periodicity in their time profiles at discrete frequencies. Estimates of the associated magnetic field strength (B) indicate that B ≈ 0.06–1 G at a typical frequency such as 19.5 MHz.

  6. INSTRUMENTS AND METHODS OF INVESTIGATION: Spectral and spectral-frequency methods of investigating atmosphereless bodies of the Solar system

    NASA Astrophysics Data System (ADS)

    Busarev, Vladimir V.; Prokof'eva-Mikhailovskaya, Valentina V.; Bochkov, Valerii V.

    2007-06-01

    A method of reflectance spectrophotometry of atmosphereless bodies of the Solar system, its specificity, and the means of eliminating basic spectral noise are considered. As a development, joining the method of reflectance spectrophotometry with the frequency analysis of observational data series is proposed. The combined spectral-frequency method allows identification of formations with distinctive spectral features, and estimations of their sizes and distribution on the surface of atmospherelss celestial bodies. As applied to investigations of asteroids 21 Lutetia and 4 Vesta, the spectral frequency method has given us the possibility of obtaining fundamentally new information about minor planets.

  7. Research of propagation the high frequency signals during total solar eclipses

    NASA Astrophysics Data System (ADS)

    Ryabova, Mariya; Ivanov, Vladimir; Ivanov, Dmitrii; Riabova, Natalia; Elsukov, Aleksei

    Vertical-oblique sounding methods are special importance for the study; they provide data on the electron concentration. In panoramic sounders, the mean frequencies of sounding signals vary consequently in the range of apriori uncertainty of the conditions of their reflection from the ionosphere. The aim of this work is the experimental study of the variations in the MUFs along one-hop HF lines during the total solar eclipses, and their application for the estimation of the effective recombination coefficient. To solve the above problem, experiments were carried out with the use of a chirp sounder manufactured at the Volga State University of Technology. The main advantages of chirp sounder are connected with the use of continuous chirps, which allow for the use of methods of optimal reception when deciphering in a frequency region, which provides for a signal-to-noise ratio acceptable for obtaining reliable results. We carried out experiments on oblique chirp sounding of the ionosphere during the total solar eclipse of March 29, 2006, and on the reference days of March 28 and 30, 2006, as well as during the total solar eclipse of August 1, 2008, and the reference days of July 31 and August 2, 2008. The ionosonde transmitters were located in Great Britain (the town of Inskip), Cyprus, and Irkutsk, and the receiver was located in Yoshkar-Ola. The maximal phases of the eclipse of March 29 at the target sounding point (TSP) were 0.89 for Cyprus-Yoshkar-Ola (observed at 11:15 UT) and 0.49 for Inskip-Yoshkar-Ola (observed at 11:03 UT); for the eclipse of August 1, 1 for Irkutsk-Yoshkar-Ola (observed at 11:36 UT). Based on the primary data (ionograms), the secondary data were determined in automatic mode. In particular, diurnal variations in the MUF of the 1F2 and 2F2 modes were calculated for the eclipse periods and the reference days along different radio paths. Variation in the MUF on the reference days required the use of a smoothing procedure, which was carried out

  8. Helioseismic Constraints on the Gradient of Angular Velocity at the Base of the Solar Convection Zone

    NASA Technical Reports Server (NTRS)

    Kosovichev, A. G.

    1996-01-01

    The layer of transition from the nearly rigid rotation of the radiative interior to the latitudinal differential rotation of the convection zone plays a significant role in the internal dynamics of the Sun. Using rotational splitting coefficients of the p-mode frequencies, obtained during 1986-1990 at the Big Bear Solar Observatory, we have found that the thickness of the transitional layer is 0.09 +/- 0.04 solar radii (63 +/- 28 Mm), and that most of the transition occurs beneath the adiabatically stratified part of the convection zone, as suggested by the dynamo theories of the 22 yr solar activity cycle.

  9. A thorough analysis of the short- and mid-term activity-related variations in the solar acoustic frequencies

    NASA Astrophysics Data System (ADS)

    Santos, A. R. G.; Cunha, M. S.; Avelino, P. P.; Chaplin, W. J.; Campante, T. L.

    2017-02-01

    The frequencies of the solar acoustic oscillations vary over the activity cycle. The variations in other activity proxies are found to be well correlated with the variations in the acoustic frequencies. However, each proxy has a slightly different time behaviour. Our goal is to characterize the differences between the time behaviour of the frequency shifts and of two other activity proxies, namely the area covered by sunspots and the 10.7-cm flux. We define a new observable that is particularly sensitive to the short-term frequency variations. We then compare the observable when computed from model frequency shifts and from observed frequency shifts obtained with the Global Oscillation Network Group (GONG) for cycle 23. Our analysis shows that on the shortest time-scales, the variations in the frequency shifts seen in the GONG observations are strongly correlated with the variations in the area covered by sunspots. However, a significant loss of correlation is still found. We verify that the times when the frequency shifts and the sunspot area do not vary in a similar way tend to coincide with the times of the maxima of the quasi-biennial variations seen in the solar seismic data. A similar analysis of the relation between the 10.7-cm flux and the frequency shifts reveals that the short-time variations in the frequency shifts follow even more closely those of the 10.7-cm flux than those of the sunspot area. However, a loss of correlation between frequency shifts and 10.7-cm flux variations is still found around the same times.

  10. Seismic Study of the Solar Interior: Inferences from SOI/MDI Observations During Solar Activity

    NASA Technical Reports Server (NTRS)

    Korzennik, Sylvain G.; Wagner, William J. (Technical Monitor)

    2001-01-01

    We have continued in collaboration with Dr. Eff-Darwich (University of La Laguna, Tenerife, Spain) the study of the structure, asphericity and dynamics of the solar interior from p-mode frequencies and frequency splittings. In March 2001, Dr. Eff-Darwich came for 3 weeks visit to CfA. During this visit we completed our work on the inversion of the internal solar rotation rate, and submitted a paper describing this work to the Astrophysical Journal. This paper has been recently revised in response to the referee comments and I expect that it will be accepted for publication very soon. We also have analyzed helioseismic data looking for temporal variations of the solar stratification near the base of the convection zone. We have expanded on the initial work that was presented at the SOHO-10/GONG-2000 meeting (October 2000, Tenerife), and are in the process of writing this up. Substantial progress towards the characterization of high-degree p-modes has been achieved. Indeed, in collaboration Dr. Rabello-Soares (Stanford University), we have gained a clear conceptual understanding of the various elements that affect the leakage matrix of the SOI/MDI instrument. This was presented in an invited talk at the SOHO-10/GONG-2000 meeting (October 2000, Tenerife). Once we will have successfully migrated from a qualitative to a quantitative assessment of these effects, we should be able to generate high-degree p-modes frequencies so crucial in the diagnostic of the layers just below solar surface.

  11. Using frequency response functions to manage image degradation from equipment vibration in the Daniel K. Inouye Solar Telescope

    NASA Astrophysics Data System (ADS)

    McBride, William R.; McBride, Daniel R.

    2016-08-01

    The Daniel K Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, providing a significant increase in the resolution of solar data available to the scientific community. Vibration mitigation is critical in long focal-length telescopes such as the Inouye Solar Telescope, especially when adaptive optics are employed to correct for atmospheric seeing. For this reason, a vibration error budget has been implemented. Initially, the FRFs for the various mounting points of ancillary equipment were estimated using the finite element analysis (FEA) of the telescope structures. FEA analysis is well documented and understood; the focus of this paper is on the methods involved in estimating a set of experimental (measured) transfer functions of the as-built telescope structure for the purpose of vibration management. Techniques to measure low-frequency single-input-single-output (SISO) frequency response functions (FRF) between vibration source locations and image motion on the focal plane are described. The measurement equipment includes an instrumented inertial-mass shaker capable of operation down to 4 Hz along with seismic accelerometers. The measurement of vibration at frequencies below 10 Hz with good signal-to-noise ratio (SNR) requires several noise reduction techniques including high-performance windows, noise-averaging, tracking filters, and spectral estimation. These signal-processing techniques are described in detail.

  12. Low-Frequency Type III Bursts and Solar Energetic Particle Events

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat; Makela, Pertti

    2010-01-01

    We analyzed the coronal mass ejections (CMEs), flares, and type 11 radio bursts associated with a set of six low frequency (<14 MHz) extended type III bursts from active region 10588. The durations were measured at 1 and 14 MHz using high resolution data from Wind/WAVES and were within the range (>15 min) normally used to define these bursts. All but one of the type III bursts was not associated with a type 11 burst in the metric or longer wavelength domains. The burst without type 11 burst also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1-MHz duration of the type III burst (28 min) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. The CMEs were of similar speeds and the flares are also of similar size and duration. This study suggests that the type III burst duration may not be a good indicator of an SEP event.

  13. Solar winds driven by nonlinear low-frequency Alfvén waves from the photosphere: Parametric study for fast/slow winds and disappearance of solar winds

    NASA Astrophysics Data System (ADS)

    Suzuki, Takeru K.; Inutsuka, Shu-Ichiro

    2006-06-01

    We investigate how properties of the corona and solar wind in open coronal holes depend on properties of magnetic fields and their footpoint motions at the surface. We perform one-dimensional magnetohydrodynamical (MHD) simulations for the heating and the acceleration in coronal holes by low-frequency Alfvén waves from the photosphere to 0.3 or 0.1 AU. We impose low-frequency (≲0.05 Hz) transverse fluctuations of the field lines at the photosphere with various amplitude, spectrum, and polarization in the open flux tubes with different photospheric field strength, Br,0, and superradial expansion of the cross section, fmax. We find that transonic solar winds are universal consequences. The atmosphere is also stably heated up to ≳106 K by the dissipation of the Alfvén waves through compressive-wave generation and wave reflection in the cases of the sufficient wave input with photospheric amplitude, ≳ 0.7 km s-1. The density, and accordingly the mass flux, of solar winds show a quite sensitive dependence on because of an unstable aspect of the heating by the nonlinear Alfvén waves. A case with = 0.4 km s-1 gives ≃50 times smaller mass flux than the fiducial case for the fast wind with = 0.7 km s-1; solar wind virtually disappears only if becomes ≃1/2. We also find that the solar wind speed has a positive correlation with Br,0/fmax, which is consistent with recent observations by Kojima et al. On the basis of these findings, we show that both fast and slow solar winds can be explained by the single process, the dissipation of the low-frequency Alfvén waves, with different sets of and Br,0/fmax. Our simulations naturally explain the observed (1) anticorrelation of the solar wind speed and the coronal temperature and (2) larger amplitude of Alfvénic fluctuations in the fast wind. In Appendix A, we also explain our implementation of the outgoing boundary condition of the MHD waves with some

  14. Annual ionospheric variations of the critical frequency foF2 at the equatorial stations during the solar minima

    NASA Astrophysics Data System (ADS)

    Biktash, Lilia

    2016-07-01

    We have analyzed annual ionospheric variations of the critical frequency foF2 at the equatorial stations during the solar minima. There are essential distinctions between the global TEC (total electron content) and foF2 annual variations during the last two solar minima. Many authors concluded that the annual means of foF2 and the global TEC were reduced, while others investigations no found essential variations as compared with the previous solar minimum. Most if not all of authors suppose that the possible source of this phenomenon is the low level of the EUV (extreme ultraviolet) during the solar minima. The aim of our paper is to amplify these conclusions or to propose new factor which can change ionosphere parameters during the solar minima. We calculated annual variations of foF2 at the equatorial stations and compared these data with Dst annual variations. We found that in addition to low level of the EUV during the solar minima, geomagnetic storms effects have to be included as the influencing factor on annual ionospheric variations.

  15. "Wind" spacecraft and ground observation of solar and near earth high-frequency radio burts during strong solar activity at november 4, 2001

    NASA Astrophysics Data System (ADS)

    Dudnik, O. V.; Kaiser, M. L.; Yurovsky, Y. F.

    2003-04-01

    The strong solar flare of X1/3B magnitude on November 4, 2001 is investigated in the radio frequency range along with its affect on near Earth space HF radio noise. The dynamic spectra of solar type II and III radio emission in the range of 20 kHz - 14 MHz from WAVES instrument of the WIND spacecraft reveals that many unresolved solar type III bursts were detected during the solar flare that were probably generated by energetic electrons at the shock front driven by a coronal mass ejection. Simultaneously, the level of radio noise was recorded at frequencies 280, 300, 150 and 500 MHz by ground radio antennae placed 700 km from each other. In spite of differences in the construction of radio receiving channels, the series of bursts were observed at both places during and after the beginning of the flare. Taking into consideration that the flare occurred during night time for both ground observing points, these bursts cannot be interpreted as solar type. The comparative analysis of the fine structure of bursts shows that there were at least two groups of bursts around the flare. The first group was weak and coincided with Ha and X-ray flare as well as with solar II type radio burst according to the WIND RAD2 receiver. The second group, brightly distinguishing above the background noise, occurred 3-4 hours after the flare. The wavelet and cross correlation analyses of radio noise at different frequencies after excluding strong spikes are provided. The obtained experimental data were compared with dynamics of electron and proton fluxes in different energetic ranges for different regions of the space: 1) in interplanetary space using data from the ACE satellite, 2) in the polar cap using "Coronas-F" satellite data, and 3) from geostationary orbit using data from the GOES satellites. Fine structure of the bursts mostly does not coincide at different frequencies suggesting either narrow band emission features or the imposing of local conditions on the radio wave

  16. Searching for narrow-band oscillations in solar flares in the presence of frequency-dependent noise

    NASA Astrophysics Data System (ADS)

    Inglis, Andrew; Ireland, Jack

    2014-06-01

    A common feature of solar flare emission is the appearance of short timescale fluctuations, often interpreted in terms of oscillatory signatures, and often referred to as quasi-periodic pulsations (QPPs) or quasi-periodic oscilations (QPOs). These fluctuations are an important diagnostic of solar plasma, as they are linked to the flare reconnection and particle acceleration sites. However, it has recently become clear that solar flare time series, like many astrophysical objects, are often dominated by frequency-dependent 'red' noise, rather than white noise. This frequency-dependent red-noise is commonly not taken into account when analyzing flare time-series for narrow-band oscillations. We demonstrate the application of a Bayesian method of searching for narrow-band oscillations in flares (based on Vaughan 2010) that fully accounts for frequency-dependent noise. We apply this method to the recent flares of 2011 February 15 and 2011 June 7, utilizing high-cadence EUV and X-ray data from the Proba-2/LYRA and Fermi/GBM instruments. While emphasizing that the observed fluctuations are a very real effect, we show that the emission from the selected events can be well described by a frequency-dependent noise model, without the need to invoke an explicit oscillatory mechanism. This presents a challenge to our current understanding of flare fluctuations, and suggests that narrow-band oscillations in flare emission may be much less prevalent than previously believed.

  17. EVIDENCE FOR HIGH-FREQUENCY QPOs WITH A 3:2 FREQUENCY RATIO FROM A 5000 SOLAR MASS BLACK HOLE

    SciTech Connect

    Pasham, Dheeraj R.; Cenko, S. Bradley; Mushotzky, Richard F.; Tombesi, Francesco; Zoghbi, Abderahmen; Miller, Jon E-mail: brad.cenko@nasa.gov E-mail: richard@astro.umd.edu E-mail: jonmm@umich.edu

    2015-09-20

    Following the discovery of 3:2 resonance quasi-periodic oscillations (QPOs) in M82X-1, we have constructed power density spectra (PDS) of all 15 (sufficiently long) XMM-Newton observations of the ultraluminous X-ray source NGC 1313 X-1 (L{sub X} ≈ 2 × 10{sup 40} erg s{sup −1}). We detect a strong QPO at a frequency of 0.29 ± 0.01 Hz in data obtained on 2012 December 16. Subsequent searching of all the remaining observations for a 3:2/2:3 frequency pair revealed a feature at 0.46 ± 0.02 Hz on 2003 December 13 (frequency ratio of 1.59 ± 0.09). The global significance of the 0.29 Hz feature considering all frequencies between 0.1 and 4 Hz is >3.5σ. The significance of the 0.46 ± 0.02 Hz QPO is >3.5σ for a search at 2/3 and 3/2 of 0.29 Hz. We also detect lower-frequency QPOs (32.9 ± 2.6 and 79.7 ± 1.2 mHz). All the QPOs are superimposed on a continuum consisting of flat-topped, band-limited noise, breaking into a power law at a frequency of 16 ± 3 mHz and white noise at ≳0.1 Hz. NGC 1313 X-1's PDS is analogous to stellar-mass black holes’ (StMBHs) PDS in the so-called steep power-law state, but with the respective frequencies (both QPOs and break frequencies) scaled down by a factor of ∼1000. Using the inverse mass-to-high-frequency QPO scaling of StMBHs, we estimate NGC 1313 X-1's black hole mass to be 5000 ± 1300 M{sub ⊙}, consistent with an inference from the scaling of the break frequency. However, the implied Eddington ratio, L{sub Edd} > 0.03 ± 0.01, is significantly lower compared to that of StMBHs in the steep power-law state (L{sub Edd} ≳ 0.2)

  18. Variability of the occurrence frequency of solar flares as a function of peak hard X-ray rate

    NASA Technical Reports Server (NTRS)

    Bai, T.

    1993-01-01

    We study the occurrence frequency of solar flares as a function of the hard X-ray peak count rate, using observations of the Solar Maximum Mission. The size distributions are well represented by power-law distributions with negative indices. As a better alternative to the conventional method, we devise a maximum likelihood method of determining the power-law index of the size distribution. We find that the power-law index of the size distribution changes with time and with the phase of the 154-day periodicity. The size distribution is steeper during the maximum years of solar cycle 21 (1980 and 1981) than during the declining phase (1982-1984). The size distribution, however, is flatter during the maximum phase of the 154-day periodicity than during the minimum phase. The implications of these findings are discussed.

  19. Static and Dynamic Characteristic Models of Global Solar Radiation Fluctuation in the Scope of Load Frequency Control

    NASA Astrophysics Data System (ADS)

    Akatsuka, Motoki; Hara, Ryoichi; Kita, Hiroyuki; Takitani, Katsuyuki; Saito, Masami

    Penetration of photovoltaic generation (PV) system into the power system may give some negative impacts to stable operations of power system; for example, to the frequency control. Therefore, investigation on the short-term fluctuation of PV generation is important as a precaution against further PV penetration. Since the PV generation is almost proportional to the incident solar radiation, this paper develops static and dynamic characteristic models for short-term fluctuation in the global solar radiation. The static characteristic model is a set of standard deviations which have been statistically estimated based on the past observed data. The dynamic characteristic model is autoregressive models which are designed for the actually observed time sequential short-term fluctuation data. In both models, the clearness index is used to eliminate seasonal variation of solar radiation.

  20. Evidence for the existence of nonradial solar oscillations: Solar rotation

    NASA Technical Reports Server (NTRS)

    Caudell, T. P.; Hill, H. A.

    1980-01-01

    The coherent properties of six oscillations over a two week period in which seven days of equatorial diameter measurements were analyzed, are confirmed by the addition of an extra day of data. The two large 1 (the principal order number in the spherical harmonic expansion of the eigenfunction) g-mode oscillations may be candidates for the slowly rotating mode locked structures. For the four low frequency p-modes, periodic nature is observed in the daily power levels, varying with periods of several days. This is attributed to beating between rotationally split m states for a given 1 value. Nonradial modes are a major contribution to the observed solar oscillations. The nonradial character of the observed modes allows the depth dependence of the internal solar rotation to be investigated.

  1. Solar pumped Nd:YAG laser efficiency enhancement using Cr:LiCAF frequency down-shifter

    NASA Astrophysics Data System (ADS)

    Payziyev, Sh.; Makhmudov, Kh.

    2016-12-01

    The possibility of increase of Nd:YAG solar pumped lasers pumping efficiency with the use of Cr:LiCAF as a solar spectrum frequency-down-shifting element is studied by the simulation calculation method. Comparative analyses of side- and end-pumping schemes are conducted. The numerical experiments have been conducted for combinations of Nd:YAG active medium and Cr:LiCAF for both side- and end-pumping configurations. It is shown that the use of Cr:LiCAF frequency down-shifter significantly increases the pumping efficiency of Nd:YAG active medium in both cases. In addition the replacement of Nd:YAG with cerium co-doped Nd:YAG have shown possibility of further increase the efficiency.

  2. Time and frequency transfer by the Master-Slave Returnable Timing System technique - Application to solar power transmission

    NASA Technical Reports Server (NTRS)

    Lindsey, W. C.; Kantak, A. V.

    1979-01-01

    The concept of the Master Slave Returnable Timing System (MSRTS) is presented which combines the advantages of the master slave (MS) and the Returnable Timing System (RTS) for time and frequency transfer. The basic idea of MSRTS is to send the time-frequency signal received at a particular node back to the sending node. The delay accumulated by this return signal is used to advance the phase of the master (sending) node thereby canceling the effect of the delay introduced by the path. The method can be used in highly accurate clock distribution systems required in avionics, computer communications, and large retrodirective phased arrays such as the Solar Power Satellite.

  3. Low frequency electromagnetic signals in the atmosphere caused by geodynamics and solar activity

    NASA Astrophysics Data System (ADS)

    Novik, Oleg; Ruzhin, Yuri; Ershov, Sergey; Volgin, Max; Smirnov, Fedor

    Due to the composed structure of the medium and large portions of energy transferred, a seismic excitation in the oceanic or continental lithosphere disturbs all types of geophysical fields. To investigate the problem of electromagnetic (EM) forcing on the atmosphere from the seismically activated lithosphere, we have formulated two mathematical models of interaction of fields of different physical nature resulting in arising of the low-frequency (from 0.1 to 10 Hz by amplitude of a few hundreds of pT) EM signals in the atmosphere. First we have considered the EM field generation in the moving oceanic lithosphere and then in the moving continental one. For both cases, the main physical principles and geological data were applied for formulation of the model and characteristics of the computed signals of different nature agree with measurements of other authors. On the basis of the 2D model of the seismo-hydro-EM-temperature interaction in a lithosphere-Ocean-atmosphere domain, a block-scheme of a multisensory vertically distributed (from a seafloor up to the ionosphere) tsunami precursors’ detection system is described. On the basis of the 3D model of the seismo-EM interaction in a lithosphere-atmosphere domain, we explain effect of location of the future seismic epicenter area (obtained by Prof. Kopytenko, Yu. A. from Inst. IZMIRAN of Russian Acad. Sci. and co-authors) as the result of the magnetic field measurements in the atmosphere near the earth’s surface. We believe that the biosphere effects of forcing on the atmosphere may not be ignored. We formulate the result of our measurements with the system of micro-voltmeters: low-frequency EM disturbances of the atmosphere caused by solar activity (namely, geomagnetic storms with the geomagnetic index values K = 5 and K = 6), are decreasing temporarily the coherence of oscillations of the electric potentials of different points on the surface of a head, i.e. the coherence of the human brain EM processes. We are

  4. A new system for observing solar oscillations at the Mount Wilson Observatory. I - System design and installation

    NASA Technical Reports Server (NTRS)

    Rhodes, E. J., Jr.; Howard, R. F.; Ulrich, R. K.; Smith, E. J.

    1983-01-01

    An observation system designed to obtain daily measurements of solar photospheric and subphotospheric rotational velocities, from the frequency splitting of nonradial solar p-mode oscillations of degree greater than 150, is nearing completion of the Mount Wilson Observatory. The system will combine a 244 x 248 pixel CID camera with a high speed floating point array processor, a 32-bit minicomputer, and a large capacity disk storage system. These components will be integrated into the spectrograph of the 60-foot solar tower telescope at Mount Wilson.

  5. Solar and geomagnetic effects on the frequency of atmospheric circulation types over Europe: an analysis based on a large number of classifications

    NASA Astrophysics Data System (ADS)

    Huth, Radan; Cahynová, Monika; Kyselý, Jan

    2010-05-01

    Recently, effects of the 11-year solar cycle on various aspects of tropospheric circulation in the Northern Hemisphere in winter have been recognized. One of our previous studies showed a significant solar effect on the frequency of synoptic types from the Hess-Brezowsky catalogue. Here, we use a large collection of varied classifications of circulation patterns, assembled within the COST733 Action "Harmonization and Applications of Weather Types Classifications for European Regions" to detect the solar effect on the frequency of synoptic types. The collection contains both objective and subjective classifications. The advantage of this multi-classification approach is that peculiarities or biases of any single classification (catalogue) that might influence the detected solar signal vanish once a large ensemble of classifications is used. We divide winter months (December to March) into three groups according to the mean monthly solar activity, quantified by the F10.7 flux. The three groups correspond to the minima of the 11-year solar cycle, a moderate solar activity, and solar maxima. Within each group, frequencies of occurrence of individual circulation types are calculated. Differences in the occurrence of individual classes between solar activity groups indicate the presence of a solar activity effect on atmospheric circulation over Europe. Statistical significance of these differences is estimated by a block resampling method. The research is supported by the Grant Agency of the Czech Academy of Sciences, project A300420805, and by the Ministry of Education, Youth, and Sports of the Czech Republic, contract OC115.

  6. Co-analysis of Solar Microwave and Hard X-Ray Spectral Evolutions. I. In Two Frequency or Energy Ranges

    NASA Astrophysics Data System (ADS)

    Song, Qiwu; Huang, Guangli; Nakajima, Hiroshi

    2011-06-01

    Solar microwave and hard X-ray spectral evolutions are co-analyzed in the 2000 June 10 and 2002 April 10 flares, and are simultaneously observed by the Owens-Valley Solar Array in the microwave band and by Yohkoh/Hard X-ray Telescope or RHESSI in the hard X-ray band, with multiple subpeaks in their light curves. The microwave and hard X-ray spectra are fitted by a power law in two frequency ranges of the optical thin part and two photon energy ranges, respectively. Similar to an earlier event in Shao & Huang, the well-known soft-hard-soft pattern of the lower energy range changed to the hard-soft-hard (HSH) pattern of the higher energy range during the spectral evolution of each subpeak in both hard X-ray flares. This energy dependence is actually supported by a positive correlation between the overall light curves and spectral evolution in the lower energy range, while it becomes an anti-correlation in the higher energy range. Regarding microwave data, the HSH pattern appears in the spectral evolution of each subpeak in the lower frequency range, which is somewhat similar to Huang & Nakajima. However, it returns back to the well-known pattern of soft-hard-harder for the overall spectral evolution in the higher frequency range of both events. This frequency dependence is confirmed by an anti-correlation between the overall light curves and spectral evolution in the lower frequency range, but it becomes a positive correlation in the higher frequency range. The possible mechanisms are discussed, respectively, for reasons why hard X-ray and microwave spectral evolutions have different patterns in different energy and frequency intervals.

  7. Multiscaling statistics of high frequency global solar radiation data in the Guadeloupean Archipelago

    NASA Astrophysics Data System (ADS)

    Calif, R.; Schmitt, F. G.; Huang, Y.; Soubdhan, T.

    2013-12-01

    The part of the solar power production from photovoltaiccs systems is constantly increasing in the electric grids. Solar energy converter devices such as photovoltaic cells are very sensitive to instantaneous solar radiation fluctuations. Thus rapid variation of solar radiation due to changes in the local meteorological condition can induce large amplitude fluctuations of the produced electrical power and reduce the overall efficiency of the system. When large amount of photovoltaic electricity is send into a weak or small electricity network such as island network, the electric grid security can be in jeopardy due to these power fluctuations. The integration of this energy into the electrical network remains a major challenge, due to the high variability of solar radiation in time and space. To palliate these difficulties, it is essential to identify the characteristic of these fluctuations in order to anticipate the eventuality of power shortage or power surge. A good knowledge of the intermittency of global solar radiation is crucial for selecting the location of a solar power plant and predicting the generation of electricity. This work presents a multifractal analysis study of 367 daily global solar radiation sequences measured with a sampling rate of 1 Hz over one year at Guadeloupean Archipelago (French West Indies) located at 16o15'N latitude and 60o30'W longitude. The mean power spectrum computed follows a power law behaviour close to the Kolmogorov spectrum. The intermittent and multifractal properties of global solar radiation data are investigated using several methods. Under this basis, a characterization for each day using three multifractal parameters is proposed.

  8. Solar plasma: Viking 1975 interplanetary spacecraft dual-frequency Doppler data

    NASA Technical Reports Server (NTRS)

    Wu, S. C.; Winn, F. B.

    1977-01-01

    Viking 1975 interplanetary S- and X-band Doppler data are surveyed. These data show consistency with differenced range versus integrated Doppler (DRVID) data when there is solar plasma and with Faraday rotation data otherwise. An increase of solar plasma effects with decreasing sun-earth-probe (SEP) angle (approaching Mars orbit insertion) is demonstrated. The 2-way/3-way data indicate a homogeneous solar plasma structure over a 8,000-km spread. Occasional cycle slips in the data are pinpointed and tabulated.

  9. Studies of the variations of the first Schumann resonance frequency during the solar flare on 7 March 2012

    NASA Astrophysics Data System (ADS)

    Zhou, Hongjuan; Qiao, Xiaolin

    2015-05-01

    The ELF measurements at the YS station in China during the X5.4 solar flare on 7 March 2012 are examined. The first modal Schumann resonance (SR) frequencies of the horizontal magnetic field components were found to increase by 0.1-0.2 Hz during the X-ray burst. During the enhancement of the proton flux, the first modal frequency of the east-west magnetic field component decreases by approximately 0.6 Hz at most, while the variation in the north-south magnetic field component is less well defined. The mechanisms of the variations are simulated with a finite difference time domain technique by modeling the perturbed conductivity profile in the day-night asymmetric Earth-ionosphere cavity and modeling the global lightning source with the raw flash data measured by satellites. The simulated varying trends of the SR frequencies observed near the ground with the altitudes of the conductivity perturbations are nearly the same as those previously reported and are interpreted by the two characteristic height model first proposed by Greifinger and Greifinger. It is concluded that the SR frequencies increase for enhanced conductivity above the altitude of 60-70 km because of the lowered magnetic height and decrease for enhanced conductivity below this altitude due to the lowered electric height. This finding can explain the opposite behaviors of the SR frequencies during X-ray bursts and strong solar proton events (SPEs). The simulation model in this work proved to be effective, with the simulated shifts in the values of SR frequencies during X-ray bursts and SPEs being close to the practical measurements.

  10. Using high frequency consumption data to identify demand response potential for solar energy integration

    NASA Astrophysics Data System (ADS)

    Jin, L.; Borgeson, S.; Fredman, D.; Hans, L.; Spurlock, A.; Todd, A.

    2015-12-01

    California's renewable portfolio standard (2012) requires the state to get 33% of its electricity from renewable sources by 2020. Increased share of variable renewable sources such as solar and wind in the California electricity system may require more grid flexibility to insure reliable power services. Such grid flexibility can be potentially provided by changes in end use electricity consumptions in response to grid conditions (demand-response). In the solar case, residential consumption in the late afternoon can be used as reserve capacity to balance the drop in solar generation. This study presents our initial attempt to identify, from a behavior perspective, residential demand response potentials in relation to solar ramp events using a data-driven approach. Based on hourly residential energy consumption data, we derive representative daily load shapes focusing on discretionary consumption with an innovative clustering analysis technique. We aggregate the representative load shapes into behavior groups in terms of the timing and rhythm of energy use in the context of solar ramp events. Households of different behavior groups that are active during hours with high solar ramp rates are identified for capturing demand response potential. Insights into the nature and predictability of response to demand-response programs are provided.

  11. FRESH INSIGHTS ON THE STRUCTURE OF THE SOLAR CORE

    SciTech Connect

    Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne; New, Roger; Serenelli, Aldo M. E-mail: w.j.chaplin@bham.ac.uk E-mail: r.new@shu.ac.uk

    2009-07-10

    We present new results on the structure of the solar core, obtained with new sets of frequencies of solar low-degree p modes obtained from the BiSON network. We find that different methods used in extracting the different sets of frequencies cause shifts in frequencies, but the shifts are not large enough to affect solar structure results. We find that the BiSON frequencies show that the solar sound speed in the core is slightly larger than that inferred from data from Michelson Doppler Imager low-degree modes, and the uncertainties on the inversion results are smaller. Density results also change by a larger amount, and we find that solar models now tend to show smaller differences in density compared to the Sun. The result is seen at all radii, a result of the fact that conservation of mass implies that density differences in one region have to cancel out density differences in others, since our models are constructed to have the same mass as the Sun. The uncertainties on the density results are much smaller too. We attribute the change in results to having more, and lower frequency, low-degree mode frequencies available. These modes provide greater sensitivity to conditions in the core.

  12. Effect of junction recombination velocity of electrical parameters of a vertical parallel silicon solar cell under frequency modulation

    NASA Astrophysics Data System (ADS)

    Sahin, Gokhan

    2016-12-01

    This study investigates a theoretical study based on the determination of electrical parameters in solar cell junction vertical parallel silicon under polychromatic illumination and frequency modulation. From the excess minority carrier's density in the solar cell, the photocurrent density and the photovoltage are derived. The route of the current voltage density ( I = f(V)) that materializes the behavior of the generator; we have a model on the shunt resistance and the series resistance. The I- V method is used to determine electrical parameters such as resistance and shunt resistance or various junction recombination velocity. From their expressions, we study their pace according to Bode and Nyquist and then extend the study to other electrical parameter. The Bode diagrams of the diffusion capacitance are shown for different junction recombination velocity.

  13. Properties of the F2-layer critical frequency median in the nocturnal subauroral ionosphere during low and moderate solar activity

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Deminov, R. G.; Shubin, V. N.

    2016-11-01

    Based on an analysis of data from the European ionospheric stations at subauroral latitudes, it has been found that the main ionospheric trough (MIT) is not characteristic for the monthly median of the F2-layer critical frequency ( foF2), at least for low and moderate solar activity. In order to explain this effect, the properties of foF2 in the nocturnal subauroral ionosphere have been additionally studied for low geomagnetic activity, when the MIT localization is known quite reliably. It has been found that at low and moderate solar activity during night hours in winter, the foF2 data from ionospheric stations are often absent in the MIT area. For this reason, a model of the foF2 monthly median, which was constructed from the remaining data of these stations, contains no MIT or a very weakly pronounced MIT.

  14. On nonlinear evolution of low-frequency Alfvén waves in weakly-expanding solar wind plasmas

    SciTech Connect

    Nariyuki, Y.

    2015-02-15

    A multi-dimensional nonlinear evolution equation for Alfvén waves in weakly-expanding solar wind plasmas is derived by using the reductive perturbation method. The expansion of solar wind plasma parcels is modeled by an expanding box model, which includes the accelerating expansion. It is shown that the resultant equation agrees with the Wentzel-Kramers-Brillouin prediction of the low-frequency Alfvén waves in the linear limit. In the cold and one-dimensional limit, a modified derivative nonlinear Schrodinger equation is obtained. Direct numerical simulations are carried out to discuss the effect of the expansion on the modulational instability of monochromatic Alfvén waves and the propagation of Alfvén solitons. By using the instantaneous frequency, it is quantitatively shown that as far as the expansion rate is much smaller than wave frequencies, effects of the expansion are almost adiabatic. It is also confirmed that while shapes of Alfvén solitons temporally change due to the expansion, some of them can stably propagate after their collision in weakly-expanding plasmas.

  15. Deka-keV X-ray observations of solar bursts with WATCH/GRANAT: frequency distributions of burst parameters

    NASA Astrophysics Data System (ADS)

    Crosby, N.; Vilmer, N.; Lund, N.; Sunyaev, R.

    1998-06-01

    Solar flare observations in the deka-keV range are performed by the WATCH experiment on board the GRANAT satellite. The WATCH experiment is presented, including the energy calibration as applied in the present work. The creation of the solar burst catalogue covering two years of observation is described and some examples of solar observations are given. The estimated energy releases in the flares presented here are found to extend below the range of hard X-ray flares which were previously studied by ISEE-3 and HXRBS/SMM detectors. The X-ray emitting component cannot be exclusively explained by contributions from a thermal plasma around a few keV. Either a hotter component or a non-thermal population of particles must also be present to produce the observed deka-keV emission. The WATCH data furthermore shows that the relative contributions of these components may change during an event or from event to event and that the injection of energy contained in suprathermal electrons may occur throughout an event and not only during the rise phase. For the most energetic WATCH flares simultaneous observations performed by other experiments at higher energies further indicate that non-thermal emission can be observed as low as 10 keV. A statistical study is performed on the total WATCH solar database and frequency distributions are built on measured X-ray flare parameters. It is also investigated how the properties of these frequency distributions behave when subgroups of events defined by different ranges of parameters are considered. No correlation is found between the elapsed time interval between successive flares arising from the same active region and the peak intensity of the flare.

  16. Why DA and DB white dwarfs do not show coronal activity and p-mode oscillations

    SciTech Connect

    Musielak, Z.E.; Fontenla, J.M. )

    1989-11-01

    The problems of nonradiative heating of outer atmospheric layers and p-mode oscillations in white dwarfs caused by acoustic waves generated in convective zones are discussed. These effects have been studied by calculating the cutoff periods for adiabatic and isothermal waves propagating in atmospheres of DA and DB stars with Teff greater than or equal 20,000 K and log g = 6-9. The obtained cutoff periods are approximately bounded by 0.01 and 40 sec for high- and low-gravity white dwarfs, respectively. Expected amplitudes of p-mode oscillations corresponding to trapped acoustic waves with small angular wave numbers are estimated, indicating that the amplitudes could be observed as Doppler shifts of spectral lines which might be detectable if adequate spectral resolution were available. The luminosity variations corresponding to these amplitudes are unlikely to be observable when all damping processes are accounted for. Results also indicate that the present theory of convection predicts some irregularities in the behavior of physical parameters. 34 refs.

  17. Why DA and DB white dwarfs do not show coronal activity and p-mode oscillations

    NASA Technical Reports Server (NTRS)

    Musielak, Z. E.; Fontenla, J. M.

    1989-01-01

    The problems of nonradiative heating of outer atmospheric layers and p-mode oscillations in white dwarfs caused by acoustic waves generated in convective zones are discussed. These effects have been studied by calculating the cutoff periods for adiabatic and isothermal waves propagating in atmospheres of DA and DB stars with Teff greater than or equal 20,000 K and log g = 6-9. The obtained cutoff periods are approximately bounded by 0.01 and 40 sec for high- and low-gravity white dwarfs, respectively. Expected amplitudes of p-mode oscillations corresponding to trapped acoustic waves with small angular wave numbers are estimated, indicating that the amplitudes could be observed as Doppler shifts of spectral lines which might be detectable if adequate spectral resolution were available. The luminosity variations corresponding to these amplitudes are unlikely to be observable when all damping processes are accounted for. Results also indicate that the present theory of convection predicts some irregularities in the behavior of physical parameters.

  18. An investigation of ground-based observations of solar oscillations at Stanford

    NASA Technical Reports Server (NTRS)

    Henning, Harald M. J.

    1987-01-01

    Data obtained in the last 8 years of solar differential Doppler observations at Stanford were considered. The four best time series of data were examined in detail. The sources of error in the data were investigated and removed where possible. In particular, the contribution resulting from transparency variations in the sky was examined. Detection method applicable to data with low signal to noise ratio and low filling factor were developed and utilized for the investigation of global solar modes of oscillations in the data. The frequencies of p-modes were measured and identified. The presence of g-modes were also determined in the Stanford data.

  19. Energetic electrons from solar flares and associated type 3 radio bursts from metric to hectometric wave frequencies

    NASA Technical Reports Server (NTRS)

    Sakurai, K.

    1972-01-01

    Distinct Kev electron events as observed by satellites near the earth are, in general, associated with solar flares which are accompained by the emission of both metric and hectometric type 3 radio bursts. The positions of these flares are mainly on the western hemisphere of the sun. These results show that Kev electrons propagate under the control of the magnetic field in the interplanetary space and that, while propagating through this space, these electrons excite type 3 radio bursts from metric to hectometric wave frequencies. Emission characteristics of hectometric type 3 bursts are briefly considered in relation to the positions of associated flares.

  20. The quasi-biennial periodicity (QBP) in velocity and intensity helioseismic observations. The seismic QBP over solar cycle 23

    NASA Astrophysics Data System (ADS)

    Simoniello, R.; Finsterle, W.; Salabert, D.; García, R. A.; Turck-Chièze, S.; Jiménez, A.; Roth, M.

    2012-03-01

    Aims: We looked for signatures of quasi-biennial periodicity (QBP) over different phases of solar cycle by means of acoustic modes of oscillation. Low-degree p-mode frequencies are shown to be sensitive to changes in magnetic activity due to the global dynamo. Recently there has been reported evidence of two-year variations in p-mode frequencies. Methods: Long high-quality helioseismic data are provided by BiSON (Birmingham Solar Oscillation Network), GONG (Global Oscillation Network Group), GOLF (Global Oscillation at Low Frequency) and VIRGO (Variability of Solar IRradiance and Gravity Oscillation) instruments. We determined the solar cycle changes in p-mode frequencies for spherical degree ℓ = 0, 1, 2 with their azimuthal components in the frequency range 2.5 mHz ≤ ν ≤ 3.5 mHz. Results: We found signatures of QBP at all levels of solar activity in the modes more sensitive to higher latitudes. The signal strength increases with latitude and the equatorial component also seems to be modulated by the 11-year envelope. Conclusions: The persistent nature of the seismic QBP is not observed in the surface activity indices, where mid-term variations are found only from time to time and mainly in periods of high activity. This feature, together with the latitudinal dependence, provides more evidence of a mechanism that is almost independent and different from the one that brings the active regions up to the surface. Therefore, these findings can be used to provide more constraints on dynamo models that consider a further cyclic component on top of the 11-year cycle.

  1. Differences of the Solar Magnetic Activity Signature in Velocity and Intensity Helioseismic Observations

    NASA Astrophysics Data System (ADS)

    Salabert, D.; García, R. A.; Jiménez, A.

    2013-12-01

    The high-quality, full-disk helioseismic observations continuously collected by the spectrophotometer GOLF and the three photometers VIRGO/SPMs onboard the SoHO spacecraft for 17 years now (since April 11, 1996, apart from the SoHO “vacations”) are absolutely unique for the study of the interior of the Sun and its variability with magnetic activity. Here, we look at the differences in the low-degree oscillation p-mode frequencies between radial velocity and intensity measurements taking into account all the known features of the p-mode profiles (e.g., the opposite peak asymmetry), and of the power spectrum (e.g., the presence of the higher degrees ℓ = 4 and 5 in the signal). We show that the intensity frequencies are higher than the velocity frequencies during the solar cycle with a clear temporal dependence. The response between the individual angular degrees is also different. Time delays are observed between the temporal variations in GOLF and VIRGO frequencies. Such analysis is important in order to put new constraints and to better understand the mechanisms responsible for the temporal variations of the oscillation frequencies with the solar magnetic activity as well as their height dependences in the solar atmosphere. It is also important for the study of the stellar magnetic activity using asteroseismic data.

  2. Radio Frequency Magnetron Sputtering Deposition of TiO2 Thin Films and Their Perovskite Solar Cell Applications.

    PubMed

    Chen, Cong; Cheng, Yu; Dai, Qilin; Song, Hongwei

    2015-12-03

    In this work, we report a physical deposition based, compact (cp) layer synthesis for planar heterojunction perovskite solar cells. Typical solution-based synthesis of cp layer for perovskite solar cells involves low-quality of thin films, high-temperature annealing, non-flexible devices, limitation of large-scale production and that the effects of the cp layer on carrier transport have not been fully understood. In this research, using radio frequency magnetron sputtering (RFMS), TiO2 cp layers were fabricated and the thickness could be controlled by deposition time; CH3NH3PbI3 films were prepared by evaporation &immersion (E &I) method, in which PbI2 films made by thermal evaporation technique were immersed in CH3NH3I solution. The devices exhibit power conversion efficiency (PCE) of 12.1% and the photovoltaic performance can maintain 77% of its initial PCE after 1440 h. The method developed in this study has the capability of fabricating large active area devices (40 × 40 mm(2)) showing a promising PCE of 4.8%. Low temperature and flexible devices were realized and a PCE of 8.9% was obtained on the PET/ITO substrates. These approaches could be used in thin film based solar cells which require high-quality films leading to reduced fabrication cost and improved device performance.

  3. Radio Frequency Magnetron Sputtering Deposition of TiO2 Thin Films and Their Perovskite Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Chen, Cong; Cheng, Yu; Dai, Qilin; Song, Hongwei

    2015-12-01

    In this work, we report a physical deposition based, compact (cp) layer synthesis for planar heterojunction perovskite solar cells. Typical solution-based synthesis of cp layer for perovskite solar cells involves low-quality of thin films, high-temperature annealing, non-flexible devices, limitation of large-scale production and that the effects of the cp layer on carrier transport have not been fully understood. In this research, using radio frequency magnetron sputtering (RFMS), TiO2 cp layers were fabricated and the thickness could be controlled by deposition time; CH3NH3PbI3 films were prepared by evaporation & immersion (E & I) method, in which PbI2 films made by thermal evaporation technique were immersed in CH3NH3I solution. The devices exhibit power conversion efficiency (PCE) of 12.1% and the photovoltaic performance can maintain 77% of its initial PCE after 1440 h. The method developed in this study has the capability of fabricating large active area devices (40 × 40 mm2) showing a promising PCE of 4.8%. Low temperature and flexible devices were realized and a PCE of 8.9% was obtained on the PET/ITO substrates. These approaches could be used in thin film based solar cells which require high-quality films leading to reduced fabrication cost and improved device performance.

  4. Radio Frequency Magnetron Sputtering Deposition of TiO2 Thin Films and Their Perovskite Solar Cell Applications

    PubMed Central

    Chen, Cong; Cheng, Yu; Dai, Qilin; Song, Hongwei

    2015-01-01

    In this work, we report a physical deposition based, compact (cp) layer synthesis for planar heterojunction perovskite solar cells. Typical solution-based synthesis of cp layer for perovskite solar cells involves low-quality of thin films, high-temperature annealing, non-flexible devices, limitation of large-scale production and that the effects of the cp layer on carrier transport have not been fully understood. In this research, using radio frequency magnetron sputtering (RFMS), TiO2 cp layers were fabricated and the thickness could be controlled by deposition time; CH3NH3PbI3 films were prepared by evaporation & immersion (E & I) method, in which PbI2 films made by thermal evaporation technique were immersed in CH3NH3I solution. The devices exhibit power conversion efficiency (PCE) of 12.1% and the photovoltaic performance can maintain 77% of its initial PCE after 1440 h. The method developed in this study has the capability of fabricating large active area devices (40 × 40 mm2) showing a promising PCE of 4.8%. Low temperature and flexible devices were realized and a PCE of 8.9% was obtained on the PET/ITO substrates. These approaches could be used in thin film based solar cells which require high-quality films leading to reduced fabrication cost and improved device performance. PMID:26631493

  5. Holocene flood frequency across the Central Alps - solar forcing and evidence for variations in North Atlantic atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Wirth, Stefanie B.; Glur, Lukas; Gilli, Adrian; Anselmetti, Flavio S.

    2013-11-01

    The frequency of large-scale heavy precipitation events in the European Alps is expected to undergo substantial changes with current climate change. Hence, knowledge about the past natural variability of floods caused by heavy precipitation constitutes important input for climate projections. We present a comprehensive Holocene (10,000 years) reconstruction of the flood frequency in the Central European Alps combining 15 lacustrine sediment records. These records provide an extensive catalog of flood deposits, which were generated by flood-induced underflows delivering terrestrial material to the lake floors. The multi-archive approach allows suppressing local weather patterns, such as thunderstorms, from the obtained climate signal. We reconstructed mainly late spring to fall events since ice cover and precipitation in form of snow in winter at high-altitude study sites do inhibit the generation of flood layers. We found that flood frequency was higher during cool periods, coinciding with lows in solar activity. In addition, flood occurrence shows periodicities that are also observed in reconstructions of solar activity from 14C and 10Be records (2500-3000, 900-1200, as well as of about 710, 500, 350, 208 (Suess cycle), 150, 104 and 87 (Gleissberg cycle) years). As atmospheric mechanism, we propose an expansion/shrinking of the Hadley cell with increasing/decreasing air temperature, causing dry/wet conditions in Central Europe during phases of high/low solar activity. Furthermore, differences between the flood patterns from the Northern Alps and the Southern Alps indicate changes in North Atlantic circulation. Enhanced flood occurrence in the South compared to the North suggests a pronounced southward position of the Westerlies and/or blocking over the northern North Atlantic, hence resembling a negative NAO state (most distinct from 4.2 to 2.4 kyr BP and during the Little Ice Age). South-Alpine flood activity therefore provides a qualitative record of variations

  6. Direct conversion of light to radio frequency energy. [using photoklystrons for solar power satellites

    NASA Technical Reports Server (NTRS)

    Freeman, J. W.; Simons, S.

    1981-01-01

    A description is presented of the test results obtained with the latest models of the phototron. The phototron was conceived as a replacement for the high voltage solar cell-high power klystron combination for the solar power satellite concept. Physically, the phototron is a cylindrical evacuated glass tube with a photocathode, two grids, and a reflector electrode in a planar configuration. The phototron can be operated either in a biased mode where a low voltage is used to accelerate the electron beam produced by the photocathode or in an unbiased mode referred to as self-oscillation. The device is easily modulated by light input or voltage to broadcast in AM or FM. The range of operation of the present test model phototrons is from 2 to 200 MHz.

  7. Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Kentischer, T. J.; Steinmetz, T.; Probst, R. A.; Franz, M.; Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Schmidt, W.

    2012-09-01

    Laser frequency combs (LFC) provide a direct link between the radio frequency (RF) and the optical frequency regime. The comb-like spectrum of an LFC is formed by exact equidistant laser modes, whose absolute optical frequencies are controlled by RF-references such as atomic clocks or GPS receivers. While nowadays LFCs are routinely used in metrological and spectroscopic fields, their application in astronomy was delayed until recently when systems became available with a mode spacing and wavelength coverage suitable for calibration of astronomical spectrographs. We developed a LFC based calibration system for the high-resolution echelle spectrograph at the German Vacuum Tower Telescope (VTT), located at the Teide observatory, Tenerife, Canary Islands. To characterize the calibration performance of the instrument, we use an all-fiber setup where sunlight and calibration light are fed to the spectrograph by the same single-mode fiber, eliminating systematic effects related to variable grating illumination.

  8. Turnover Frequency in Solar Microwave Bursts with an Extremely Flat Optically Thin Spectrum

    NASA Astrophysics Data System (ADS)

    Song, Q. W.; Nakajima, H.; Huang, G. L.; Tan, B. L.; Huang, Y.; Wu, Z.

    2016-12-01

    Four microwave bursts have been selected from the Nobeyama Radio Polarimeter (NoRP) observations with an extremely flat spectrum in the optically thin part and a very hard spectral index between 0 and -1 in the maximum phase of all bursts. It is found that the time evolution of the turnover frequency is inversely proportional to the time profiles of the radio flux in all bursts. Based on the nonthermal gyrosynchrotron theory of Ramaty ( Astrophys. J. 158, 753, 1969), the local magnetic field strength and the electron spectral index are calculated uniquely from the observed radio spectral index and the turnover frequency. We found that the electron energy spectrum is very hard (spectral index 1 - 2), and the time variation of the magnetic field strength is also inversely proportional to the radio flux as a function of time in all bursts. Hence, the time evolution of the turnover frequency can be explained directly by its dependence on the local magnetic field strength. The high turnover frequency (several tens of GHz) is mainly caused by a strong magnetic field of up to several hundred gauss, and probably by the Razin effect under a high plasma density over 10^{10} cm^{-3} in the maximum phase of these bursts. Therefore, the extremely flat microwave spectrum can be well understood by the observed high turnover frequency and the calculated hard electron spectral index.

  9. Ultra Low-Frequency Oscillations of a Solar Filament Observed by the GONG Network

    NASA Astrophysics Data System (ADS)

    Efremov, V. I.; Parfinenko, L. D.; Solov'ev, A. A.

    2016-11-01

    The data of ground-based telescopes of the Global Oscillation Network Group (GONG) obtained in the Hα line provide an opportunity to study the long-period oscillations of chromospheric filaments (quiescent prominences). For the first time, on the basis of time series of 5 days duration that we combined from the observations of three observatories of the GONG network, a new ultra-low mode with a period of between 20 and 30 hours was reliably detected in oscillations of a long-lived dark filament on the solar disk.

  10. Ionospheric error contribution to GNSS single-frequency navigation at the 2014 solar maximum

    NASA Astrophysics Data System (ADS)

    Orus Perez, Raul

    2017-04-01

    For single-frequency users of the global satellite navigation system (GNSS), one of the main error contributors is the ionospheric delay, which impacts the received signals. As is well-known, GPS and Galileo transmit global models to correct the ionospheric delay, while the international GNSS service (IGS) computes precise post-process global ionospheric maps (GIM) that are considered reference ionospheres. Moreover, accurate ionospheric maps have been recently introduced, which allow for the fast convergence of the real-time precise point position (PPP) globally. Therefore, testing of the ionospheric models is a key issue for code-based single-frequency users, which constitute the main user segment. Therefore, the testing proposed in this paper is straightforward and uses the PPP modeling applied to single- and dual-frequency code observations worldwide for 2014. The usage of PPP modeling allows us to quantify—for dual-frequency users—the degradation of the navigation solutions caused by noise and multipath with respect to the different ionospheric modeling solutions, and allows us, in turn, to obtain an independent assessment of the ionospheric models. Compared to the dual-frequency solutions, the GPS and Galileo ionospheric models present worse global performance, with horizontal root mean square (RMS) differences of 1.04 and 0.49 m and vertical RMS differences of 0.83 and 0.40 m, respectively. While very precise global ionospheric models can improve the dual-frequency solution globally, resulting in a horizontal RMS difference of 0.60 m and a vertical RMS difference of 0.74 m, they exhibit a strong dependence on the geographical location and ionospheric activity.

  11. Ionospheric error contribution to GNSS single-frequency navigation at the 2014 solar maximum

    NASA Astrophysics Data System (ADS)

    Orus Perez, Raul

    2016-11-01

    For single-frequency users of the global satellite navigation system (GNSS), one of the main error contributors is the ionospheric delay, which impacts the received signals. As is well-known, GPS and Galileo transmit global models to correct the ionospheric delay, while the international GNSS service (IGS) computes precise post-process global ionospheric maps (GIM) that are considered reference ionospheres. Moreover, accurate ionospheric maps have been recently introduced, which allow for the fast convergence of the real-time precise point position (PPP) globally. Therefore, testing of the ionospheric models is a key issue for code-based single-frequency users, which constitute the main user segment. Therefore, the testing proposed in this paper is straightforward and uses the PPP modeling applied to single- and dual-frequency code observations worldwide for 2014. The usage of PPP modeling allows us to quantify—for dual-frequency users—the degradation of the navigation solutions caused by noise and multipath with respect to the different ionospheric modeling solutions, and allows us, in turn, to obtain an independent assessment of the ionospheric models. Compared to the dual-frequency solutions, the GPS and Galileo ionospheric models present worse global performance, with horizontal root mean square (RMS) differences of 1.04 and 0.49 m and vertical RMS differences of 0.83 and 0.40 m, respectively. While very precise global ionospheric models can improve the dual-frequency solution globally, resulting in a horizontal RMS difference of 0.60 m and a vertical RMS difference of 0.74 m, they exhibit a strong dependence on the geographical location and ionospheric activity.

  12. Frequency Drift Rate Investigation of Solar Radio Burst Type II Due to Coronal Mass Ejections Occurrence on 4th November 2015 Captured by CALLISTO at Sumedang-Indonesia

    NASA Astrophysics Data System (ADS)

    Batubara, M.; Manik, T.; Suryana, R.; Lathif, M.; Sitompul, P.; Zamzam, M.; Mumtahana, F.

    2017-03-01

    The formations type of solar radio bursts can be known base on the frequency range that is detected. The CALLISTO system works with a wide band of the frequency making it possible to detect several types of solar burst. Indonesia exactly at Sumedang, CALLISTO system detected the formation of solar radio bursts forms of type II for the first time on 5 November 2014. On the other side, CALLISTO spectrometer detects and traces the phenomenon of CME (Coronal Mass Ejections) which causes the solar radio burst type II occurrence. In this paper will be calculated frequency drift rate during the occurrence of solar radio bursts of type II phenomenon on 4th November 2015 at 03:30 UT. The results of these calculations will be discussed as a related study of drift rate during the phenomenon of burst type II radio bursts associated with CME. The obtained drift rate during the solar radio bursts events above 2.8 MHz / s with low drift rate so that the speed of the CME that occurred only about 790 km / s as shown from LASCO.

  13. Propagation of solar oscillations to secondary cosmic radiation

    NASA Astrophysics Data System (ADS)

    Haley, C.; Thomson, D. J.

    2013-12-01

    Neutron monitor data show periodic modulation of cosmic rays entering Earth's atmosphere from the 11-year solar cycle. However, neutron data is peculiar for a counting process because on shorter time scales their variance is less than the average. We investigate neutron monitor spectra for evidence that solar modes, systematic solar oscillations of the sun's interior, contribute to periodic variability in cosmic ray intensity on Earth. Accurate modal frequencies are given in Broomhall, MNRAS. 396 (2009). Though the interplanetary medium is widely accepted as turbulent, Thomson et al. [1] have shown that signatures of the solar normal modes of oscillation coexist with turbulence in interplanetary charged particle flux data from the Ulysses and Voyager spacecraft. Subsequent studies have strengthened these claims [2]. We show peaks in Bartol Research Institute neutron monitor spectra which agree with candidate mode frequencies in the p-mode band (250-5100μHz) and exhibit characteristic mode splittings due to solar rotation. The figure shows part of the spectrum of 10-s neutron count data from July-September 2005. This spectrum has 48 peaks above the 99.9% significance level in the band, whereas for random data one expects ~2.2 peaks. Additionally, we find significant peaks with modal splittings above the 5100μHz acoustic cutoff. [1] Thomson et al., Propagation of solar oscillations through the interplanetary medium, Nature. 376 (1995). [2] Thomson et al., Solar modal structure of the engineering environment, IEEE. 95 (2007).

  14. Statistical aspects of the 1980 solar flars. 1: Data base, frequency distributions, and overview remarks

    NASA Technical Reports Server (NTRS)

    Wilson, R. M.

    1982-01-01

    AII1349 H alpha flares occurring in 1980 which have known start, maximum brightness, and end times, latitudes, and associated importance and X-ray classes were used to perform a statistical study of flare rise time, decay time, duration, latitude, importance (areal and relative intensity), and X-ray class. Frequency distributions of these parameters are tabulated and plotted.

  15. A solar plasma stream measured by DRVID and dual-frequency range and Doppler radio metric data

    NASA Technical Reports Server (NTRS)

    Winn, F. B.; Wu, S. C.; Komarek, T. A.; Lam, V. W.; Royden, H. N.; Yip, K. B. W.

    1977-01-01

    S- and X-band DRVID, S- and X-band dual-frequency range (SX(p)), and Doppler (SX(p)) measured a 15-fold increase in the line-of-sight electron content of the solar plasma above the normal plasma background. A general increase in the plasma electron content continued for nearly 50 hours: it started about 12:00 (GMT) on 12 March 1976 and continued to grow until 17:00 (GMT) on 14 March. For the next 55 hours, between 17:00 (GMT) on 14 March to 00:54 (GMT) on 17 March, the plasma level diminished as the background level was approached. Not only were the temporal changes and absolute level of the plasma content measured but the measurements were also used to ascertain the mean-plasma-concentration location: it was estimated to be 4.1 light minutes from earth.

  16. A Novel Hybrid Statistical Particle Swarm Optimization for Multimodal Functions and Frequency Control of Hybrid Wind-Solar System

    NASA Astrophysics Data System (ADS)

    Verma, Harish Kumar; Jain, Cheshta

    2016-09-01

    In this article, a hybrid algorithm of particle swarm optimization (PSO) with statistical parameter (HSPSO) is proposed. Basic PSO for shifted multimodal problems have low searching precision due to falling into a number of local minima. The proposed approach uses statistical characteristics to update the velocity of the particle to avoid local minima and help particles to search global optimum with improved convergence. The performance of the newly developed algorithm is verified using various standard multimodal, multivariable, shifted hybrid composition benchmark problems. Further, the comparative analysis of HSPSO with variants of PSO is tested to control frequency of hybrid renewable energy system which comprises solar system, wind system, diesel generator, aqua electrolyzer and ultra capacitor. A significant improvement in convergence characteristic of HSPSO algorithm over other variants of PSO is observed in solving benchmark optimization and renewable hybrid system problems.

  17. Geometry of low-frequency solar wind magnetic turbulence: Evidence for radially aligned Alfénic fluctuations

    NASA Astrophysics Data System (ADS)

    Saur, Joachim; Bieber, John W.

    1999-05-01

    We employ ``omnitape'' magnetic field data to determine the geometry of low-frequency (5- to 12-hour timescales) magnetic fluctuations in the solar wind. We consider three axisymmetric geometries, slab, two-dimensional (2-D), and isotropic, as well as binary combinations of them. Both the radial direction and the mean magnetic field direction are considered as candidate symmetry axes. We apply simultaneously three different tests for distinguishing these geometries. Our analysis decisively favors a binary geometry composed of 2-D turbulence symmetric with respect to the mean field direction and slab turbulence symmetric with respect to the radial direction. The presence of a slab component with radial symmetry provides observational support for a long-standing theoretical prediction of radially aligned Alfvénic fluctuations at 1 AU. We also find a variation of turbulence properties with solar wind speed, such that magnetic fluctuations in slow wind are more energetic and possess a greater proportion of slab modes than those in fast wind, and the ratio of longitudinal to transverse power in the 2-D component increases with wind speed.

  18. An estimate of the coronal magnetic field near a solar coronal mass ejection from low-frequency radio observations

    SciTech Connect

    Hariharan, K.; Ramesh, R.; Kishore, P.; Kathiravan, C.; Gopalswamy, N.

    2014-11-01

    We report ground-based, low-frequency (<100 MHz) radio imaging, spectral, and polarimeter observations of the type II radio burst associated with the solar coronal mass ejection (CME) that occurred on 2013 May 2. The spectral observations indicate that the burst has fundamental (F) and harmonic (H) emission components with split-band and herringbone structures. The imaging observations at 80 MHz indicate that the H component of the burst was located close to leading edge of the CME at a radial distance of r ≈ 2 R {sub ☉} in the solar atmosphere. The polarimeter observations of the type II burst, also at 80 MHz, indicate that the peak degree of circular polarization (dcp) corresponding to the emission generated in the corona ahead of and behind the associated MHD shock front are ≈0.05 ± 0.02 and ≈0.1 ± 0.01, respectively. We calculated the magnetic field B in the above two coronal regions by adopting the empirical relationship between the dcp and B for the harmonic plasma emission and the values are ≈(0.7-1.4) ± 0.2 G and ≈(1.4-2.8) ± 0.1 G, respectively.

  19. A HIGH-FREQUENCY TYPE II SOLAR RADIO BURST ASSOCIATED WITH THE 2011 FEBRUARY 13 CORONAL MASS EJECTION

    SciTech Connect

    Cho, K.-S.; Kim, R.-S.; Gopalswamy, N.; Kwon, R.-Y.; Yashiro, S.

    2013-03-10

    We examine the relationship between the high-frequency (425 MHz) type II radio burst and the associated white-light coronal mass ejection (CME) that occurred on 2011 February 13. The radio burst had a drift rate of 2.5 MHz s{sup -1}, indicating a relatively high shock speed. From SDO/AIA observations we find that a loop-like erupting front sweeps across high-density coronal loops near the start time of the burst (17:34:17 UT). The deduced distance of shock formation (0.06 Rs) from the flare center and speed of the shock (1100 km s{sup -1}) using the measured density from SDO/AIA observations are comparable to the height (0.05 Rs, from the solar surface) and speed (700 km s{sup -1}) of the CME leading edge observed by STEREO/EUVI. We conclude that the type II burst originates even in the low corona (<59 Mm or 0.08 Rs, above the solar surface) due to the fast CME shock passing through high-density loops.

  20. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    SciTech Connect

    Michael Klopf, J.; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sérgio

    2014-08-10

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed 'double spectra'. Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  1. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    SciTech Connect

    Klopf, J. Michael; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sergio

    2014-07-01

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed "double spectra." Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  2. THE FREQUENCY OF HOT JUPITERS ORBITING NEARBY SOLAR-TYPE STARS

    SciTech Connect

    Wright, J. T.; Marcy, G. W.; Howard, A. W.; Johnson, John Asher; Morton, T. D.; Fischer, D. A.

    2012-07-10

    We determine the fraction of F, G, and K dwarfs in the solar neighborhood hosting hot Jupiters as measured by the California Planet Survey from the Lick and Keck planet searches. We find the rate to be 1.2% {+-} 0.38%, which is consistent with the rate reported by Mayor et al. from the HARPS and CORALIE radial velocity (RV) surveys. These numbers are more than double the rate reported by Howard et al. for Kepler stars and the rate of Gould et al. from the OGLE-III transit search; however, due to small number statistics these differences are of only marginal statistical significance. We explore some of the difficulties in estimating this rate from the existing RV data sets and comparing RV rates to rates from other techniques.

  3. Variable low-frequency radio emission of the solar system and galactic objects

    NASA Astrophysics Data System (ADS)

    Konovalenko, Alexander; Kolyadin, Vladimir; Rucker, Helmut; Zakharenko, Vyacheslav; Zarka, Philippe; Griessmeier, Jean-M.; Denis, Loran; Melnik, Valentin; Litvinenko, Galina; Zaitsev, Valerij; Falkovich, Igor; Ulyanov, Oleg; Sidorchuk, Mikhail; Stepkin, Sergej; Stanislavskij, Alexander; Kalinichenko, Nikolaj; Boiko, Nastja; Vasiljiva, Iaroslavna; Mukha, Dmytro; Koval, Artem

    2013-04-01

    There are many physical processes and propagation effects for the producing the time variable radio emission just at the low frequencies (at the decameter wavelength). The study of this radio emission is the important part of the modern radio astronomy. Strong progress in the development of the radio telescopes, methods and instrumentation allowed to start the corresponding investigations at new quality and quantity levels. It related to the implementation of the world largest UTR-2 radio telescope (effective area is more than 100 000 sq.m) more high sensitive at frequencies less than 30 MHz. During last years many new observations were carried out with this radio telescope and many new effects have been detected for the Sun, planets, interplanetary medium, exoplanets as well as various kinds of the stars.

  4. Hindcast and forecast of grand solar minina and maxima using a three-frequency dynamo model based on Jupiter-Saturn tidal frequencies modulating the 11-year sunspot cycle

    NASA Astrophysics Data System (ADS)

    Scafetta, Nicola

    2016-04-01

    The Schwabe frequency band of the Zurich sunspot record since 1749 is found to be made of three major cycles with periods of about 9.98, 10.9 and 11.86 years. The two side frequencies appear to be closely related to the spring tidal period of Jupiter and Saturn (range between 9.5 and 10.5 years, and median 9.93 years) and to the tidal sidereal period of Jupiter (about 11.86 years). The central cycle can be associated to a quasi-11-year sunspot solar dynamo cycle that appears to be approximately synchronized to the average of the two planetary frequencies. A simplified harmonic constituent model based on the above two planetary tidal frequencies and on the exact dates of Jupiter and Saturn planetary tidal phases, plus a theoretically deduced 10.87-year central cycle reveals complex quasi-periodic interference/beat patterns. The major beat periods occur at about 115, 61 and 130 years, plus a quasi-millennial large beat cycle around 983 years. These frequencies and other oscillations appear once the model is non-linearly processed. We show that equivalent synchronized cycles are found in cosmogenic records used to reconstruct solar activity and in proxy climate records throughout the Holocene (last 12,000 years) up to now. The quasi-secular beat oscillations hindcast reasonably well the known prolonged periods of low solar activity during the last millennium such as the Oort, Wolf, Sporer, Maunder and Dalton minima, as well as the 17 115-year long oscillations found in a detailed temperature reconstruction of the Northern Hemisphere covering the last 2000 years. The millennial cycle hindcasts equivalent solar and climate cycles for 12,000 years. Finally, the harmonic model herein proposed reconstructs the prolonged solar minima that occurred during 1900- 1920 and 1960-1980 and the secular solar maxima around 1870-1890, 1940-1950 and 1995-2005 and a secular upward trending during the 20th century: this modulated trending agrees well with some solar proxy model, with

  5. An instability due to the nonlinear coupling of p-modes to g-modes: Implications for coalescing neutron star binaries

    SciTech Connect

    Weinberg, Nevin N.; Arras, Phil; Burkart, Joshua

    2013-06-01

    A weakly nonlinear fluid wave propagating within a star can be unstable to three-wave interactions. The resonant parametric instability is a well-known form of three-wave interaction in which a primary wave of frequency ω {sub a} excites a pair of secondary waves of frequency ω {sub b} + ω {sub c} ≅ ω {sub a}. Here we consider a nonresonant form of three-wave interaction in which a low-frequency primary wave excites a high-frequency p-mode and a low-frequency g-mode such that ω {sub b} + ω {sub c} >> ω {sub a}. We show that a p-mode can couple so strongly to a g-mode of similar radial wavelength that this type of nonresonant interaction is unstable even if the primary wave amplitude is small. As an application, we analyze the stability of the tide in coalescing neutron star binaries to p-g mode coupling. We find that the equilibrium tide and dynamical tide are both p-g unstable at gravitational wave frequencies f {sub gw} ≳ 20 Hz and drive short wavelength p-g mode pairs to significant energies on very short timescales (much less than the orbital decay time due to gravitational radiation). Resonant parametric coupling to the tide is, by contrast, either stable or drives modes at a much smaller rate. We do not solve for the saturation of the p-g instability and therefore we cannot say precisely how it influences the evolution of neutron star binaries. However, we show that if even a single daughter mode saturates near its wave breaking amplitude, the p-g instability of the equilibrium tide will (1) induce significant orbital phase errors (Δφ ≳ 1 radian) that accumulate primarily at low frequencies (f {sub gw} ≲ 50 Hz) and (2) heat the neutron star core to a temperature of T ∼ 10{sup 10} K. Since there are at least ∼100 unstable p-g daughter pairs, Δφ and T are potentially much larger than these values. Tides might therefore significantly influence the gravitational wave signal and electromagnetic emission from coalescing neutron star binaries

  6. Radio-frequency magnetron triode sputtering of cadmium telluride and zinc telluride films and solar cells

    NASA Astrophysics Data System (ADS)

    Sanford, Adam Lee

    The n-CdS/p-CdTe solar cell has been researched for many years now. Research groups use a variety of processes to fabricate thin-film CdS/CdTe cells, including physical vapor deposition, chemical vapor deposition, and RF diode sputtering. One of the central areas of investigation concerning CdS/CdTe cells is the problem of a Schottky barrier at the back contact. Even cells fabricated with ohmic back contacts degrade into Schottky barriers as the devices are used. This severely degrades power generation. One possible solution is to use p+-ZnTe as an interlayer between CdTe and the back contact. ZnTe is easily doped with Cu to be p-type. However, even contacts with this ZnTe interlayer degrade over time, because Cu is highly mobile and diffuses away from the contact towards the CdS/CdTe junction. Another possibility is to dope ZnTe with N. It has been demonstrated using molecular beam epitaxy and RF diode sputtering. In this study, CdTe films are fabricated using a variation of RF diode sputtering called triode sputtering. This technique allows for control of ion bombardment to the substrate during deposition. Also, a higher plasma density near the target is achieved allowing depositions at lower pressures. These films are characterized structurally to show the effects of the various deposition parameters. N-doped ZnTe films are also fabricated using this technique. These films are characterized electrically to show the effects of the various deposition parameters. Also, the effects of post-deposition annealing are observed. It is found that annealing at the right temperature can increase the conductivity of the films by a factor of 3 or more. However, annealing at higher temperatures decreases the conductivity to as low as 12% of the initial conductivity. Finally, RF triode sputtered N-doped ZnTe films are used as an interlayer at the back contact of a CdS/CdTe solar cell. The effects of annealing the device before and after contact deposition are observed

  7. A new class of solar burst with MM-wave emission but only at the highest frequency (90 GHz)

    NASA Technical Reports Server (NTRS)

    Kaufmann, P.; Correia, E.; Costa, J. E. R.; Vaz, A. M. Z.; Dennis, B. R.

    1984-01-01

    High sensitivity and high time resolution solar observations at 90 GHz (lambda = 3.3 mm) have identified a unique impulsive burst on May 21, 1984 with emission that was more intense at this frequency than at lower frequencies. The first major time structure of the burst was over 10 times more intense at 90 GHz than at 30 GHz, 7 GHz, or 2.8 GHz.Only 6 seconds later, the 30 GHz impulsive structures started to be observed but still with lower intensity than at 90 GHz. Hard X-ray time structures at energies above 25 keV were almost identical to the 90 GHZ structures (to better than one second). All 90 GHz major time structures consisted of trains of multiple subsecond pulses with rise times as short as 0.03 sec and amplitudes large compared to the mean flux. When detectable, the 30 GHz subsecond pulses had smaller relative amplitude and were in phase with the corresponding 90 GHz pulses.

  8. 1-eV GaInNAs solar cells for ultrahigh-frequency multijunction devices

    SciTech Connect

    Friedman, D.J.; Geisz, J.F.; Kurtz, S.R.; Olson, J.M.

    1998-09-01

    The authors demonstrate working prototypes of a GaInNAs-based solar cell lattice-matched to GaAs with photoresponse down to 1 eV. This device is intended for use as the third junction of future-generation ultrahigh-efficiency three- and four-junction devices. Under the AM1.5 direct spectrum with all the light higher in energy than the GaAs band gap filtered out, the prototypes have open-circuit voltages ranging from 0.35 to 0.44 V, short-circuit currents of 1.8 mA/cm{sup 2}, and fill factors from 61--66%. The short-circuit currents are of principal concern: the internal quantum efficiencies rise only to about 0.2. The authors discuss the short diffusion lengths which are the reason for this low photocurrent. As a partial workaround for the poor diffusion lengths, they demonstrate a depletion-width-enhanced variation of one of the prototype devices that grades off decreased voltage for increased photocurrent, with a short-circuit current of 6.5 mA/cm{sup 2} and an open-circuit voltage of 0.29 V.

  9. Frequencies of solar activity in laminated anhydrite of Upper Permian age (Zechstein-cycle 2)

    NASA Astrophysics Data System (ADS)

    Hiete, M.; Berner, U.

    2003-04-01

    Upper Permian Zechstein contains seven evaporitic cycles that were deposited in an epicontinental sea expanding from E-England to Poland. Zechstein-cycles 1 to 3 show a sequence of marine pelite, overlain by marine carbonate and evaporites (in the order sulfate, halite containing possibly anhydrite and potassium salts, and regressive sulphate at the top). Whereas the marginal facies of the lower sulphate horizon of Zechstein-cycle 2 (Stassfurt cycle) consists of massive anhydrite, its basin facies shows in the lower part a fine lamination of white anhydrite alternating with thin black organic carbon rich layers. These laminations are supposed to be annually deposited layers. The black laminae originate from the annual bloom of algae. Layer thickness is about 0.4 to 1.0 mm and increases from basin centre to more marginal positions. The individual layers can be traced over 300 km within the NW-German Basin. The previously described variability of layer thickness requires a forcing mechanism that is effective over long distances and must be also highly periodic. Also, varying layer thicknesses indicate varying anhydrite precipitation, i. e. probably changes in water temperatures which in turn point to climatic influences on the deposition of the layers. Here we re-examined records of cycle thickness (up to 700 laminae) determined by G. Richter-Bernburg in the 1950ties using modern techniques of time series analysis, e. g. wavelet analysis. We could detect cycles with periods of 10-14 years and 90 years which are close to known cycles of solar activity.

  10. RADIAL DEPENDENCE OF THE FREQUENCY BREAK BETWEEN FLUID AND KINETIC SCALES IN THE SOLAR WIND FLUCTUATIONS

    SciTech Connect

    Bruno, R.; Trenchi, L.

    2014-06-01

    We investigate the radial dependence of the spectral break separating the inertial from the dissipation range in power density spectra of interplanetary magnetic field fluctuations, between 0.42 and 5.3 AU, during radial alignments between MESSENGER and WIND for the inner heliosphere and between WIND and ULYSSES for the outer heliosphere. We found that the spectral break moves to higher and higher frequencies as the heliocentric distance decreases. The radial dependence of the corresponding wavenumber is of the kind κ {sub b} ∼ R {sup –1.08}, in good agreement with that of the wavenumber derived from the linear resonance condition for proton cyclotron damping. These results support conclusions from previous studies which suggest that a cyclotron-resonant dissipation mechanism must participate in the spectral cascade together with other possible kinetic noncyclotron-resonant mechanisms.

  11. The Transport of Low-Frequency Turbulence in Astrophysical Flows. II. Solutions for the Super-Alfvenic Solar Wind

    NASA Astrophysics Data System (ADS)

    Adhikari, L.; Zank, G. P.; Bruno, R.; Telloni, D.; Hunana, P.; Marino, R.; Hu, Q.

    2015-12-01

    Zank et al. 2012 developed a low-frequency turbulence transport model for any magnetized inhomogeneous flow. The model describes the energy corresponding to forward and backward propagating modes, the residual energy, and the correlation lengths corresponding to forward and backward propagating modes and the residual energy. We apply the Zank et al. model to the super-Alfvénic solar wind, considering i) the heliosphere from 0.29 to 5 AU with and without the Alfvén velocity, and ii) the entire heliosphere from 0.29 to 100 AU in the absence of the Alfvén velocity. The model shows that (1) shear driving is responsible for the in situ generation of backward propagating modes, (2) the inclusion of the background magnetic field modifies the transport of turbulence in the inner heliosphere, (3) the correlation lengths of forward and backward propagating modes are almost equal beyond ˜30 AU, and (4) the fluctuating magnetic and kinetic energies in MHD turbulence are in approximate equipartition beyond ˜30 AU. Model results for each case are compared to observations, using Helios 2 and Ulysses observations for the first case, and Voyager 2 data for the second case. For the Voyager 2 observations, we calculate the turbulent quantities corresponding to a positive and negative sign of B_r and B_t, and the azimuthal angle φ=tan-1(B_t /B_r ). The model reproduces the observations quite well from 0.29 to 5 AU. The outer heliosphere (>1 AU) observations are well described by the model. The temporal and latitudinal dependence of the observations makes a detailed comparison difficult but the overall trends are well captured by the models. We conclude that the results reasonably validate the Zank et al. model for the super-Alfvénic solar wind.

  12. Magnetic Clouds at/near the 2007 - 2009 Solar Minimum: Frequency of Occurrence and Some Unusual Properties

    NASA Astrophysics Data System (ADS)

    Lepping, R. P.; Wu, C.-C.; Berdichevsky, D. B.; Szabo, A.

    2011-12-01

    Magnetic clouds (MCs) have been identified for the period 2007 - 2009 (at/near the recent solar minimum) from Wind data, then confirmed through MC parameter fitting using a force-free model. A dramatic increase in the frequency of occurrence of these events took place from the two early years of 2007 (with five MCs) and 2008 (one MC) compared to 2009 (12 MCs). This pattern approximately mirrors the occurrence-frequency profile that was observed over a three-year interval 12 years earlier, with eight events in 1995, four in 1996, and 17 in 1997, but decreased overall by a factor of 0.62 in number. However, the average estimated axial field strength [<| B O|>] taken over all of the 18 events of 2007 - 2009 (called the “recent period” here) was only 11.0 nT, whereas <| B O|> for the 29 events of 1995 - 1997 (called the “earlier period”) was 16.5 nT. This 33% average drop in <| B O|> is more or less consistent with the decreased three-year average interplanetary magnetic field intensity between these two periods, which shows a 23% drop. In the earlier period, the MCs were clearly of mixed types but predominantly of the South-to-North type, whereas those in the recent period are almost exclusively the North-to-South type; this change is consistent with global solar field changes predicted by Bothmer and Rust ( Geophys. Monogr. Ser. 99, 139, 1997). As we have argued in earlier work (Lepping and Wu, J. Geophys. Res. 112, A10103, 2007), this change should make it possible to carry out (accurate short-term) magnetic storm forecasting by predicting the latter part of an MC from the earlier part, using a good MC parameter-fitting model with real-time data from a spacecraft at L1, for example. The recent set’s average duration is 15.2 hours, which is a 27% decrease compared to that of the earlier set, which had an average duration of 20.9 hours. In fact, all physical aspects of the recent MC set are shown to drop with respect to the earlier set; e.g., as well as the

  13. Effects of density fluctuations on nonlinear evolution of low-frequency Alfven waves in solar wind plasmas

    NASA Astrophysics Data System (ADS)

    Nariyuki, Y.; Seough, J.

    2015-12-01

    It is well known that low-frequency Alfven waves are unstable to parametric instabilities, in which these waves are nonlinearly coupled with density fluctuations [e.g, Nariyuki+Hada, JGR, 2007 and references therein]. In solar wind plasmas, low-frequency fluctuations with non-zero cross-helicity are frequently observed [e.g., Bruno+Carbone, Living Rev. Solar Phys. (2013) and references therein]. When the absolute values of normalized cross helicities are close to the unity, the fluctuations may be composed of uni-directionally (anti-sunward) propagating Alfven waves. The derivative nonlinear Schrodinger equation (DNLS) has been known as the mode of modulational instabilities of unidirectional Alfven waves [Mio et al, JPSJ, 1976; Mjolhus, JPP, 1976]. In the DNLS, the density fluctuations are assumed to be the quasi-static state, which is determined according to the ponderomotive force of envelope-modulated Alfven waves. The DNLS was extended to include the obliquely propagating, compressional component of magnetic field by Mjolhus and Wyller (JPP, 1988). The kinetically modified DNLS (KDNLS) has also been discussed by many authors [Rogister, POF, 1971; Mjolhus and Wyller, Phys. Scr, 1986; JPP, 1988; Spangler, POF B, 1989; 1990; Medvedev+Diamond, POP, 1996; Nariyuki et al, POP, 2013]. On the other hand, ion acoustic modes [Hada, 1993], large scale inhomogeneity of plasmas [Buti et al, APJ, 1999; Nariyuki, POP, 2015] and random density fluctuations [Ruderman, POP, 2002] can also affect nonlinear evolution of Alfven waves. At the present time, combined effects of these effects are not fully understood. In this presentation, we discuss two models: one of them is the model including both ion kinetic effects and ion acoustic mode and another is the model including finite thermal effects and random density fluctuations. In the former case, ion kinetic effects on both longitudinal [Nariyuki+Hada, JPSJ, 2007] and transverse modulational instabilities are discussed, while the

  14. The effect of the Mihalas, Hummer, and Daeppen equation of state and the molecular opacity on the standard solar model

    NASA Technical Reports Server (NTRS)

    Kim, Y.-C.; Demarque, P.; Guenther, D. B.

    1991-01-01

    Improvements to the Yale Rotating Stellar Evolution Code (YREC) by incorporating the Mihalas-Hummer-Daeppen equation of state, an improved opacity interpolation routine, and the effects of molecular opacities, calculated at Los Alamos, have been made. the effect of each of the improvements on the standard solar model has been tested independently by computing the corresponding solar nonradial oscillation frequencies. According to these tests, the Mihalas-Hummer-Daeppen equation of state has very little effect on the model's low l p-mode oscillation spectrum compared to the model using the existing analytical equation of state implemented in YREC. On the other hand, the molecular opacity does improve the model's oscillation spectrum. The effect of molecular opacity on the computed solar oscillation frequencies is much larger than that of the Mihalas-Hummer-Daeppen equation of state. together, the two improvements to the physics reduce the discrepancy with observations by 10 microHz for the low l modes.

  15. SEARCH FOR GLOBAL f-MODES AND p-MODES IN THE {sup 8}B NEUTRINO FLUX

    SciTech Connect

    Lopes, Ilídio E-mail: ilopes@uevora.pt

    2013-11-01

    The impact of global acoustic modes on the {sup 8}B neutrino flux time series is computed for the first time. It is shown that the time fluctuations of the {sup 8}B neutrino flux depend on the amplitude of acoustic eigenfunctions in the region where the {sup 8}B neutrino flux is produced: modes with low n (or order) that have eigenfunctions with a relatively large amplitude in the Sun's core strongly affect the neutrino flux; conversely, modes with high n that have eigenfunctions with a minimal amplitude in the Sun's core have a very small impact on the neutrino flux. It was found that the global modes with a larger impact on the {sup 8}B neutrino flux have a frequency of oscillation in the interval 250 μHz to 500 μHz (or a period in the interval 30 minutes to 70 minutes), such as the f-modes (n = 0) for the low degrees, radial modes of order n ≤ 3, and the dipole mode of order n = 1. Their corresponding neutrino eigenfunctions are very sensitive to the solar inner core and are unaffected by the variability of the external layers of the solar surface. If time variability of neutrinos is observed for these modes, it will lead to new ways of improving the sound speed profile inversion in the central region of the Sun.

  16. Discrete time--frequency coupling between the interplanetary magnetic field and the magnetosphere

    NASA Astrophysics Data System (ADS)

    Thomson, D. J.; Lessard, M. R.

    2003-12-01

    Recent work has shown the existence at geosynchronous orbit of wave power at frequencies substantially below that of fundamental field-line resonances. The existence of spectral power below that of fundamental frequencies indicates that the driver must be external to the magnetosphere, i.e, that the source is contained in the solar wind. Other work has shown that frequencies matching field-line resonances can sometimes also be observed in the solar wind. The combined spectrum that includes power at fundamental frequencies and lower overlaps with p-mode helioseismic oscillations and the question has been raised whether these helioseismic modes may stimulate the magnetospheric fluctuations. In this study, we compute coherences between the magnetometers on {ACE} and {GOES-10}, that is in interplanetary space and inside the magnetosphere. These show several frequencies where all nine coherences are significant. Moreover, many of these frequencies are the same as those reported from Ulysses data in Thomson, Maclennan, and Lanzerotti (1995). Using hourly average data from all 1999, a frequency tolerance of 30 nHz, and retaining only peaks in the coherence above the 95% significance level, about 21 agreements would be expected by chance but 34 are observed. The coherences exhibit seasonal dependence, so the coupling has a complicated time--frequency structure exhibiting both frequency and event dependence.

  17. Global fitting of power spectra of solar-like stars

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Appourchaux, T.

    2004-01-01

    Helioseismology has been able to provide the internal structure of the Sun and its dynamics. These inferences have been made possible by inverting the frequencies and rotational splitting of the p-mode oscillations. Thanks to asteroseismology, similar results can now be obtained for stars other than the Sun. For this purpose, we are developing a numerical code for global fitting of power spectra. The code is currently developed and tested on full-disk integrated solar data obtained with the SOHO/LOI instrument. It will then be applied to synthetic data from the hare-and-hound exercises of COROT. The final goal is to apply the technique to data of solar-like stars obtained with the COROT and Eddington satellites to infer the internal structure and dynamics of those stars.

  18. Solar Forbidden Oxygen, Revisited

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    2008-10-01

    Recent large reductions in the solar oxygen abundance, based on synthesis of photospheric O I, OH, and CO absorptions with 3D convection models, have provoked consternation in the helioseismology community: the previous excellent agreement between measured p-mode oscillation frequencies and predictions based on the recommended epsilonO of a decade ago (680 parts per million [ppm] relative to hydrogen) unravels at the new low value (460 ppm). In an attempt to reconcile these conflicting results, the formation of pivotal [O I] λ6300, which is blended with a weak Ni I line, has been reconsidered, exploiting an alternative 3D model (albeit only a single temporal snapshot). And while there are several areas of agreement with the earlier [O I] studies of Allende Prieto, Asplund, and others, there is one crucial point of disagreement: the epsilonO derived here is significantly larger, 650 +/- 65 ppm (although at the expense of a ~30% weaker Ni I line than expected from the recommended nickel abundance). One innovation is a more robust treatment of the solar wavelengths: the balance between the components of the [O I] + Ni I blend is sensitive to velocity errors of only a few hundred m s-1. A second improvement is enforcement of a "continuum calibration" to ensure a self-consistent 3D temperature scale. Because of the renewed agreement between the linchpin tracer [O I] and seismic oxygen, the proposed downward slump of the solar metallicity and the perceived "oxygen crisis" now can be said to rest on less secure footings.

  19. Resolving the source of the solar acoustic oscillations: What will be possible with DKIST?

    NASA Astrophysics Data System (ADS)

    Rast, Mark; Martinez Pillet, Valentin

    2016-05-01

    The solar p-modes are likely excited by small-scale convective dynamics in the solar photosphere, but the detailed source properties are not known. Theoretical models differ and observations are yet unable to differentiate between them. Resolving the underlying source events is more than a curiosity. It is important to the veracity of global helioseismic measurements (including local spectral methods such as ring diagram analysis) because global p-mode line shapes and thus accurate frequency determinations depend critically on the relationship between intensity and velocity during the excitation events. It is also fundamental to improving the accuracy of the local time-distance measurements because in these kernel calculations depend on knowledge of the source profile and the properties of the excitation noise. The Daniel K. Inouye Solar Telescope (DKIST) will have the spatial resolution and spectral range needed to resolve the solar acoustic excitation events in both time and space (horizontally and with height) using multi-wavelength observations. Inversions to determine the dynamic and thermodynamic evolution of the discrete small-scale convective events that serve as acoustic sources may also be possible, though determination of the pressure fluctuations associated with the sources is a challenge. We describe the DKIST capabilities anticipated and the preliminary work needed to prepare for them.

  20. Evolutionary models and the p-mode oscillation spectrum of Alpha Centauri A and B

    NASA Technical Reports Server (NTRS)

    Edmonds, Peter; Cram, Lawrence; Demarque, Pierre; Guenther, D. B.; Pinsonneault, Marc H.

    1992-01-01

    Spectroscopically observed abundances of Furenlid and Meylan (1990) and Los Alamos Opacity Library opacities specifically constructed for this mixture are used to construct the most detailed models to date for Alpha Cen A and B. Models including the effects of the diffusion of helium in Alpha Cen A's interior were constructed. Although the effect of helium diffusion is small in Alpha Cen A, it is slightly larger than in the sun because of the larger mass and therefore shallower convection zone of Alpha Cen A. Keeping the heavy-element mixture unchanged but varying Z within the uncertainties yields limits to the helium abundance of Y = 0.295 and 0.305, respectively. The derived age of Alpha Cen is 4.6 +/-0.4 Gyr, very similar to the solar age of 4.5 Gyr.

  1. Invoking the frequency dependence in square modulated light intensity techniques for the measurement of electron time constants in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Ghaithan, Hamid M.; Qaid, Saif M.; Hezam, Mahmoud; Siddique, Muhemmad B.; Bedja, Idriss M.; Aldwayyana, Abdullah S.

    2015-08-01

    Dye-sensitized solar cells (DSSCs) have been considered as one of the most promising new generation solar cells. Enormous research efforts have been invested to improve the efficiency of solar energy conversion which is determined by the light harvesting efficiency, electron injection efficiency and undesirable electron lifetime. A simple, cheap and trustable laser-induced photovoltage and photocurrent decay (LIPVCD) technique is adopted in this work in order to determine the electron lifetime (τe) and electron transport (τtr) in DSSCs. In LIPVCD technique, DSSC is illuminated by a small squared intensity-modulated laser beam. Time-based response of the DSSC is recorded using a transient digitized oscilloscope for further analysis. Frequency-based response was also investigated in this work. The frequency-dependent measurements turned out to be a powerful method to determine electron time constants in a fast, real-time fashion. Measurements were carried out using a standard dye-sensitized solar cell, and results were in excellent agreement with results obtained from traditional IMVS-MPS measurements. Measurements were also performed for a variety of DSSCs, having various electrodes including TiO2 nanoparticles, TiO2 nanosheets with exposed {001} facets and ZnO vertically aligned nanowires. Results will also be presented and discussed in this work.

  2. Stellar magnetic activity and variability of oscillation parameters: An investigation of 24 solar-like stars observed by Kepler

    NASA Astrophysics Data System (ADS)

    Kiefer, René; Schad, Ariane; Davies, Guy; Roth, Markus

    2017-02-01

    Context. The Sun and solar-like stars undergo activity cycles for which the underlying mechanisms are not well understood. The oscillations of the Sun are known to vary with its activity cycle and these changes provide diagnostics on the conditions below the photosphere. Kepler has detected solar-like oscillations in hundreds of stars but as of yet, no widespread detection of signatures of magnetic activity cycles in the oscillation parameters of these stars have been reported. Aims: We analysed the photometric short cadence Kepler time series of a set of 24 solar-like stars, which were observed for at least 960 d each, with the aim to find signatures of stellar magnetic activity in the oscillation parameters. Methods: We analyse the temporal evolution of oscillation parameters by measuring mode frequency shifts, changes in the height of the p-mode envelope, as well as granulation timescales. Results: For 23 of the 24 investigated stars, we find significant frequency shifts in time. We present evidence for magnetic activity in six of these stars. We find that the amplitude of the frequency shifts decreases with stellar age and rotation period. For KIC 8006161 (the most prominent example), we find that frequency shifts are smallest for the lowest and largest for the highest p-mode frequencies, as they are for the Sun. Conclusions: These findings show that magnetic activity can be routinely observed in the oscillation parameters for solar-like stars, which opens up the possibility of placing the solar activity cycle in the context of other stars by asteroseismology.

  3. Anomalous parts on the lunar crater size - frequency curve, their prediction and comparison of the lunar and solar discs granulation patterns

    NASA Astrophysics Data System (ADS)

    Kochemasov, G. G.

    Knowing that orbits make structures through warping action of inertia-gravity waves arising in celestial bodies due to their movements in non-round elliptical orbits one can use as a scale this sequence of planets with corresponding to their orbital frequencies sizes of tectonic granulation higher frequency -- finer granulation Sun s photosphere pi R 60 Mercury pi R 16 Venus pi R 6 Earth pi R 4 Mars pi R 2 asteroids pi R 1 R-a body radius But the planets have only one orbit in the Solar system Not like them satellites have 2 orbits This increases a number of tectonic granule sizes to at least 4 as one have to consider 2 main frequencies around planet and Sun and 2 modulated side frequencies division and multiplication of the higher frequency by the lower one The best studied satellite in the Solar system is the Moon with its perfectly elaborated the crater size-frequency curve it was presumed that all considered craters on its surface are of an impact origin But numerous images of the Moon acquired by cosmic missions show that this curve is not a simple one as it comprises many craters of non-impact for example of wave interference induced origin This is proved by calculating sizes of craters corresponding to main and side modulated orbital frequencies and plotting them on the classic crater size-frequency curve It appears that this curve has anomalously high number of craters exactly at ranges calculated by the wave approach namely at 80-140 and more than 600 km in diameter corresponding to the main

  4. Study of the lacustrine phytoplankton productivity dependence on solar radiation, on the basis of direct high-frequency measurements

    NASA Astrophysics Data System (ADS)

    Provenzale, Maria; Ojala, Anne; Heiskanen, Jouni; Erkkilä, Kukka-Maaria; Mammarella, Ivan; Hari, Pertti; Vesala, Timo

    2016-04-01

    One of the main components of the carbon cycle in lakes is phytoplankton. Its in situ photosynthesis and respiration are usually studied with traditional methods (dark and light bottle method, 14C labelling technique). These methods, relying on sampling and incubation, may lead to unrealistic results. They also have a poor temporal resolution, which does not allow the non-linear relationship between photosynthetically active solar radiation (PAR) and photosynthesis to be properly investigated. As a consequence, the phytoplankton net primary productivity (NPP) cannot be parameterised as a function of ambient variables. In 2008 an innovative free-water approach was proposed. It is based on non-dispersive infrared air CO2 probes that, by building an appropriate system, can be used to measure the CO2 concentration in the water at a high-frequency. At that time, the method was tested only on 3 days of data. Here, we deployed it on a boreal lake in Finland for four summers, in order to calculate the NPP and verify its dependence on PAR. The set-up was completed by an eddy-covariance system and water PAR and temperature sensors. In analogy with the procedure typically used in terrestrial ecology, we obtained the phytoplankton NPP computing the mass balance of CO2 in the mixed layer of the lake, i.e. the superficial layer where the conditions are homogeneous and most of the photosynthetic activity takes place. After calculating the NPP , we verified its dependence on PAR. The theoretical model we used was a saturating Michaelis-Menten curve, in which the variables are water temperature and PAR. The equation also contains parameters typical of the phytoplankton communities, which represent their maximum potential photosynthetic rate, their half-saturation constant and their basal respiration. These parameters allow the NPP to be parameterised as a function of T and PAR. For all the analysed year, we found a very good agreement between theory and data (R2 ranged from 0.80 to

  5. The quest for the solar g modes

    NASA Astrophysics Data System (ADS)

    Appourchaux, T.; Belkacem, K.; Broomhall, A.-M.; Chaplin, W. J.; Gough, D. O.; Houdek, G.; Provost, J.; Baudin, F.; Boumier, P.; Elsworth, Y.; García, R. A.; Andersen, B. N.; Finsterle, W.; Fröhlich, C.; Gabriel, A.; Grec, G.; Jiménez, A.; Kosovichev, A.; Sekii, T.; Toutain, T.; Turck-Chièze, S.

    2010-02-01

    Solar gravity modes (or g modes)—oscillations of the solar interior on which buoyancy acts as the restoring force—have the potential to provide unprecedented inference on the structure and dynamics of the solar core, inference that is not possible with the well-observed acoustic modes (or p modes). The relative high amplitude of the g-mode eigenfunctions in the core and the evanesence of the modes in the convection zone make the modes particularly sensitive to the physical and dynamical conditions in the core. Owing to the existence of the convection zone, the g modes have very low amplitudes at photospheric levels, which makes the modes extremely hard to detect. In this article, we review the current state of play regarding attempts to detect g modes. We review the theory of g modes, including theoretical estimation of the g-mode frequencies, amplitudes and damping rates. Then we go on to discuss the techniques that have been used to try to detect g modes. We review results in the literature, and finish by looking to the future, and the potential advances that can be made—from both data and data-analysis perspectives—to give unambiguous detections of individual g modes. The review ends by concluding that, at the time of writing, there is indeed a consensus amongst the authors that there is currently no undisputed detection of solar g modes.

  6. Radial and latitudinal gradients in the solar internal angular velocity

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain G.; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

    1988-01-01

    The frequency splittings of intermediate-degree (3 to 170 deg) p-mode oscillations obtained from a 16-day subset of observations were analyzed. Results show evidence for both radial and latitudinal gradients in the solar internal angular velocity. From 0.6 to 0.95 solar radii, the solar internal angular velocity increases systematically from 440 to 463 nHz, corresponding to a positive radial gradient of 66 nHz/solar radius for that portion of the solar interior. Analysis also indicates that the latitudinal differential rotation gradient which is seen at the solar surface persists throughout the convection zone, although there are indications that the differential rotation might disappear entirely below the base of the convection zone. The analysis was extended to include comparisons with additional observational studies and between earlier results and the results of additional inversions of several of the observational datasets. All the comparisons reinforce conclusions regarding the existence of radial and latitudinal gradients in the internal angular velocity.

  7. Solar flare soft-X-ray spectra from Very Low Frequency observations of ionospheric modulations: Possibility of uninterrupted observation of non-thermal electron-plasma interaction in solar atmosphere.

    NASA Astrophysics Data System (ADS)

    Palit, Sourav; Chakrabarti, Sandip Kumar; Ray, Suman

    2016-07-01

    The hard and soft X-ray regions of a solar flare spectrum are the manifestation of interaction, namely of bremsstrahlung radiation of the non-thermal electrons moving inward in the denser part of the solar atmosphere with the plasma heated by those energetic electrons. The continuous and uninterrupted knowledge of X-ray photon spectra of flares are of great importance to derive information on the electron acceleration and hence time-evolution of energy transport and physics during solar flares. Satellite observations of solar X-ray spectrum are often limited by the restricted windows in each duty cycle to avoid the interaction of detectors and instruments with harmful energetic charge particles. In this work we have tried to tackle the problem by examining the possibility of using Earth's ionosphere and atmosphere as the detector of such transient events. Earth's lower ionosphere and upper atmosphere are the places where the X-rays and gamma-rays from such astronomical sources are absorbed. The electron-ion production rates due to the ionization of such energetic photons at different heights depend on the intensity and wavelength of the injected spectra and hence vary from one source to another. Obviously the electron and ion density vs. altitude profile has the imprint of the incident photon spectrum. As a preliminary exercise we developed a novel deconvolution method to extract the soft X-ray part of spectra of some solar flares of different classes from the electron density profiles obtained from Very Low Frequency (VLF) observation of lower ionosphere during those events. The method presented here is useful to carry out a similar exercise to infer the higher energy part of solar flare spectra and spectra of more energetic events such as the GRBs, SGRs etc. with the possibilities of probing even lower parts of the atmosphere.

  8. Frequency fluctuations in the solar corona investigated with radio sounding experiments on the spacecraft ROSETTA and MARS EXPRESS in 2010/2011

    NASA Astrophysics Data System (ADS)

    Efimov, A. I.; Lukanina, L. A.; Samoznaev, L. N.; Chashei, I. V.; Bird, M. K.; Pätzold, M.

    2017-03-01

    Coronal radio-sounding experiments were carried out using two-way coherent dual-frequency carrier signals of the ESA spacecraft ROSETTA in 2010 and MARS EXPRESS in 2010/2011. Differential frequency measurements recorded at both NASA and ESA tracking stations (sample rate: 1 Hz) are analyzed in this paper. Spectral analysis of the S-band, X-band, and differential frequency records has shown that the r.m.s. frequency fluctuation of each signal can be described by a radial power-law function of the form σi = Ai(R/R⊙)-βi, where i = s, x, sx. The ratio of the coefficients As and Ax differs from the expected theoretical value As/Ax = fs/fx. This occurs because the X-band fluctuations underlie two-way propagation conditions while the S-band fluctuations are essentially the product of a one-way propagation experiment. The intensity of the frequency fluctuations decreases sharply at high heliolatitudes. The asymmetry of the frequency fluctuation intensity between ingress and egress is exploited to determine the solar wind speed at small heliocentric distances.

  9. What Can We Learn on the Structure and the Dynamics of the Solar Core with g Modes?

    NASA Astrophysics Data System (ADS)

    Mathur, S.; Ballot, J.; Eff-Darwich, A.; García, R. A.; Jiménez-Reyes, S. J.; Korzennik, S. G.; Turck-Chièze, S.

    2009-12-01

    The detection of the signature of dipole gravity modes has opened the path to study the solar inner radiative zone. Indeed, g modes should be the best probes to infer the properties of the solar nuclear core that represents more than half of the total mass of the Sun. Concerning the dynamics of the solar core, we can study how future observations of individual g modes could enhance our knowledge of the rotation profile of the deep radiative zone. Applying inversions on a set of real p-mode splittings coupled with either one or several g modes, we have checked the improvement of the inferred rotation profile when different error bars are considered for the g modes. Moreover, using a new methodology based on the analysis of the almost constant separation of the dipole gravity modes, we can introduce new constraints on solar models. For that purpose, we can compare g-mode predictions computed from several models including different physical inputs with the g-mode asymptotic signature detected in Global Oscillations at Low Frequencies (GOLF) data and calculate the correlation. This work shows the great consistency between the signature of dipole gravity modes and our knowledge of p-modes: incompatibility of data with a present standard model including the Asplund composition.

  10. THE QUASI-BIENNIAL PERIODICITY AS A WINDOW ON THE SOLAR MAGNETIC DYNAMO CONFIGURATION

    SciTech Connect

    Simoniello, R.; Turck-Chieze, S.; Baldner, C.; Finsterle, W.

    2013-03-10

    Manifestations of the solar magnetic activity through periodicities of about 11 and 2 years are now clearly seen in all solar activity indices. In this paper, we add information about the mechanism driving the 2-year period by studying the time and latitudinal properties of acoustic modes that are sensitive probes of the subsurface layers. We use almost 17 years of high-quality resolved data provided by the Global Oscillation Network Group to investigate the solar cycle changes in p-mode frequencies for spherical degrees l from 0 to 120 and 1600 {mu}Hz {<=}{nu} {<=} 3500 {mu}Hz. For both periodic components of solar activity, we locate the origin of the frequency shift in the subsurface layers and find evidence that a sudden enhancement in amplitude occurs in just the last few hundred kilometers. We also show that, in both cases, the size of the shift increases toward equatorial latitudes and from minimum to maximum solar activity, but, in agreement with previous findings, the quasi-biennial periodicity (QBP) causes a weaker shift in mode frequencies and a slower enhancement than that caused by the 11-year cycle. We compare our observational findings with the features predicted by different models, that try to explain the origin of this QBP and conclude that the observed properties could result from the beating between a dipole and quadrupole magnetic configuration of the dynamo.

  11. Crowdsourcing a Spatial Temporal Study of Low Frequency (LF) Propagation Effects Due to a Total Solar Eclipse: Engaging Students and Citizens in STEM

    NASA Astrophysics Data System (ADS)

    Lumsden, N. A.; Lukes, L.; Nelson, J.; Liles, W. C.; Kerby, K. C.; Crowov, F.; Rockway, J.

    2015-12-01

    The first experiments to study the effects of a solar eclipse on radio wave propagation were done in 1912 utilizing Low Frequency (LF; 30 - 300 kHz) radio waves at a handful of sites across Europe before any theory of the ionosphere had been confirmed and even before the word "ionosphere" existed. In the 1920s, a large cooperative experiment was promoted in the U.S. by Scientific American magazine. They collected over 2000 reports of AM broadcast stations from throughout the U.S. Unfortunately, many of the submissions were unusable because they lacked critical information such as date, time or location. We propose to use the 2017 solar eclipse over the continental U.S. to conduct the first wide-area LF propagation study. To perform this study, we plan to crowdsource the collection of the data by engaging student groups, citizens, and the scientific community. The tools for the different collection stations will consist of a simple homemade antenna, a simple receiver to convert the radio frequency (RF) signals to audio frequencies and a smart phone app. By using the time, date and location features of the smart phone, the problems experienced in the Scientific American experiment will be minimized. By crowdsourcing the observation sites, a number of different short, medium and long-paths studies can be obtained as the total eclipse crosses the continental U.S. The transmitter for this experiment will be WWVB located near Fort Collins, Colorado on 60.000 kHz. This is a U.S. frequency standard that is operated by NIST and transmits time codes. A second frequency, 55.500 kHz transmitted by a LF station in Dixon, CA is also being considered for this experiment. We will present an overall strategy for recruiting participants/crowdsourcing the RF collections during the 2017 total solar eclipse. Preliminary coverage calculations will be presented for WWVB and Dixon, as well as path loss calculations that can be expected during the solar eclipse condition. We will also

  12. X-rays and solar proton event induced changes in the first mode Schumann resonance frequency observed at a low latitude station Agra, India

    NASA Astrophysics Data System (ADS)

    Singh, Birbal; Tyagi, Rajesh; Hobara, Yasuhide; Hayakawa, Masashi

    2014-06-01

    Effects of two events of X-ray bursts followed by solar proton events (SPEs) occurred on 22 September, 2011 and 06 July, 2012 on the variation of first mode Schumann resonance (SR) frequency monitored at a low latitude station, Agra (Geograph. lat. 27.2°N, long. 78°E) India are examined. The variation of average first mode SR frequency shows a sudden increase in coincidence with the X-ray bursts and a decrease associated with the peak flux of SPE. The increases in the frequency in the two cases are 8.4% and 10.9% and corresponding decreases are 4.3% and 3.3% respectively. The increases in the frequency are interpreted in terms of growth of ionization in the upper part of D-region ionosphere due to X-ray bursts and decreases during SPE are caused by the high ionization in the lower D-region (altitude about 50-60 km) in the polar region. The variation of SR frequency is observed to be consistent with other observatories at middle and high latitudes. The effects of X-ray flares on the D-region of the ionosphere at low and equatorial latitudes are also examined by analyzing the amplitude data of VLF transmitter signal (NWC, f=19.8 kHz) monitored at Agra. The flare effect observed prior to sun-set hours shows increase of electron density above 60 km in the ionosphere.

  13. Validation of solar-cycle changes in low-degree helioseismic parameters from the Birmingham Solar-Oscillations Network

    NASA Astrophysics Data System (ADS)

    Howe, R.; Davies, G. R.; Chaplin, W. J.; Elsworth, Y. P.; Hale, S. J.

    2015-12-01

    We present a new and up-to-date analysis of the solar low-degree p-mode parameter shifts from the Birmingham Solar-Oscillations Network over the past 22 years, up to the end of 2014. We aim to demonstrate that they are not dominated by changes in the asymmetry of the resonant peak profiles of the modes and that the previously published results on the solar-cycle variations of mode parameters are reliable. We compare the results obtained using a conventional maximum-likelihood estimation algorithm and a new one based on the Markov Chain Monte Carlo (MCMC) technique, both taking into account mode asymmetry. We assess the reliability of the solar-cycle trends seen in the data by applying the same analysis to artificially generated spectra. We find that the two methods are in good agreement. Both methods accurately reproduce the input frequency shifts in the artificial data and underestimate the amplitude and width changes by a small amount, around 10 per cent. We confirm earlier findings that the frequency and line width are positively correlated, and the mode amplitude anticorrelated, with the level of solar activity, with the energy supplied to the modes remaining essentially unchanged. For the mode asymmetry the correlation with activity is marginal, but the MCMC algorithm gives more robust results than the MLE (Maximum-Likelihood Estimate). The magnitude of the parameter shifts is consistent with earlier work. There is no evidence that the frequency changes we see arise from changes in the asymmetry, which would need to be much larger than those observed in order to give the observed frequency shift.

  14. The Scattering of f- and p-modes from Ensembles of Thin Magnetic Flux Tubes: An Analytical Approach

    NASA Astrophysics Data System (ADS)

    Hanson, Chris S.; Cally, Paul S.

    2014-08-01

    Motivated by the observational results of Braun, we extend the model of Hanson & Cally to address the effect of multiple scattering of f and p modes by an ensemble of thin vertical magnetic flux tubes in the surface layers of the Sun. As in the observational Hankel analysis, we measure the scatter and phase shift from an incident cylindrical wave in a coordinate system roughly centered in the core of the ensemble. It is demonstrated that although thin flux tubes are unable to interact with high-order fluting modes individually, they can indirectly absorb energy from these waves through the scatters of kink and sausage components. It is also shown how the distribution of absorption and phase shift across the azimuthal order m depends strongly on the tube position as well as on the individual tube characteristics. This is the first analytical study into an ensembles multiple-scattering regime that is embedded within a stratified atmosphere.

  15. RELATIONSHIP BETWEEN THE SHELL-AVERAGED ENERGY SPECTRUM AND THE FREQUENCY SPECTRUM MEASURED BY A SINGLE SPACECRAFT IN THE SOLAR WIND

    SciTech Connect

    Podesta, J. J.

    2009-05-10

    The relationship between the shell-averaged energy spectrum E(k) and the frequency spectrum P(f) measured by a single spacecraft is needed in studies of solar wind turbulence to allow comparisons between theory and experiment. This relationship is derived for a three-dimensional (scalar) wavevector spectrum of the power-law form that is either isotropic or cylindrically symmetric about the mean magnetic field. In the latter case, it is assumed that the power-law exponents in directions parallel and perpendicular to the mean magnetic field are the same, an assumption that allows the analysis to be performed analytically. The results show that the effects of anisotropy are small when the angle {theta} {sub BV} between the solar wind velocity and the mean magnetic field is between approximately 35 deg. and 90 deg. The largest effects occur near 0 deg. where a significant correction factor is needed compared to the isotropic case due to the lower energy in the k {sub ||} direction compared to the k {sub perpendicular} direction. For solar wind spectra with an unknown degree of anisotropy, measurements of E(k) obtained when 35 deg. {<=} {theta} {sub BV} {<=} 90 deg. should be reasonably accurate for most purposes since even if the spectrum is assumed to be isotropic and no corrections are made for spectral anisotropy, the resulting errors are typically less than 10% or 20%.

  16. A simple method for correcting spatially resolved solar intensity oscillation observations for variations in scattered light

    NASA Technical Reports Server (NTRS)

    Jefferies, S. M.; Duvall, T. L., Jr.

    1991-01-01

    A measurement of the intensity distribution in an image of the solar disk will be corrupted by a spatial redistribution of the light that is caused by the earth's atmosphere and the observing instrument. A simple correction method is introduced here that is applicable for solar p-mode intensity observations obtained over a period of time in which there is a significant change in the scattering component of the point spread function. The method circumvents the problems incurred with an accurate determination of the spatial point spread function and its subsequent deconvolution from the observations. The method only corrects the spherical harmonic coefficients that represent the spatial frequencies present in the image and does not correct the image itself.

  17. Frequency dependent capacitance studies of the CdS/Cu2S thin-film solar cell

    NASA Astrophysics Data System (ADS)

    Hmurcik, L. V.; Serway, R. A.

    1982-05-01

    The dark capacitance of CdS cells has been measured as a function of both bias voltage and operating signal frequency. Results indicate a frequency dependence of the dark current capacitance which can be attributed to deep trapping states in the bulk CdS and at the interface; these states can be characterized by a time constant in the simple relaxation model. Photocapacitance measurements indicate that hole trapping takes place in a narrow region of the i layer near the Cu2S/CdS junction. The results are interpreted in terms of a frequency-dependent model proposed by Schibli and Milnes (1968). It is shown that the simple planar junction model commonly used to describe the CdS cell is accurate at high frequencies.

  18. Inverse problem in ionospheric science: prediction of solar soft-X-ray spectrum from very low frequency radiosonde results

    NASA Astrophysics Data System (ADS)

    Palit, S.; Ray, S.; Chakrabarti, S. K.

    2016-05-01

    X-rays and gamma-rays from astronomical sources such as solar flares are mostly absorbed by the Earth's atmosphere. Resulting electron-ion production rate as a function of height depends on the intensity and wavelength of the injected spectrum and therefore the effects vary from one source to another. In other words, the ion density vs. altitude profile has the imprint of the incident photon spectrum. In this paper, we investigate whether we can invert the problem uniquely by deconvolution of the VLF amplitude signal to obtain the details of the injected spectrum. We find that it is possible to do this up to a certain accuracy. This leads us to the possibility of uninterrupted observation of X-ray photon spectra of solar flares that are often hindered by the restricted observation window of space satellites to avoid charge particle damages. Such continuous means of observation are essential in deriving information on time evolution of physical processes related to electron acceleration and interaction with plasma in solar atmosphere. Our method is useful to carry out a similar exercise to infer the spectra of more energetic events such as the Gamma Ray Bursts (GRBs), Soft Gamma-ray Repeaters (SGRs) etc., by probing even the lower part of the Earth's atmosphere. We thus show that to certain extent, the Earth's atmosphere could be used as a gigantic detector of relatively strong astronomical events.

  19. Prediction soft-X-ray spectrum of solar flares from Very Low Frequency observations: an inverse problem in ionospheric science

    NASA Astrophysics Data System (ADS)

    Palit, Sourav; Chakrabarti, Sandip Kumar; Ray, Suman

    2016-07-01

    Earth's lower ionosphere and upper atmosphere absorb X-rays and gamma-rays from astronomical sources such as solar flares, Short Gamma ray Repeaters (SGRs) or Gamma Ray Bursts (GRBs). The electron-ion production rates due to the ionization of such energetic photons at different heights depend on the intensity and wavelength of the injected spectrum and hence vary from one source to another. Obviously the ion density vs. altitude profile has the imprint of the incident photon spectrum. In this paper, we examine the possibility of inverting the electron density-height profiles uniquely by deconvolution of the VLF amplitude signal to obtain information on the injected spectrum. We have been able to reproduce the soft-X-ray part of the injected spectra from two different classes of solar flares with satisfactory accuracy. With the possibilities of probing even lower parts of the atmosphere, the method presented here is useful to carry out a similar exercise to infer the higher energy part of solar flare spectra and spectra of more energetic events such as the GRBs, SGRs etc. We show that to a certain accuracy, the Earth's atmosphere may be used as a gigantic detector of relatively strong ionizing extra-terrestrial events.

  20. Towards solar activity maximum 24 as seen by GOLF and VIRGO/SPM instruments

    NASA Astrophysics Data System (ADS)

    García, R. A.; Salabert, D.; Mathur, S.; Régulo, C.; Ballot, J.; Davies, G. R.; Jiménez, A.; Simoniello, R.

    2013-06-01

    All p-mode parameters vary with time as a response to the changes induced by the cyclic behavior of solar magnetic activity. After the unusual long solar-activity minimum between cycles 23 and 24 -where the p-mode parameters have shown a different behavior than the surface magnetic proxies- we analyze the temporal variation of low-degree p-mode parameters measured by GOLF (in velocity) and VIRGO (in intensity) Sun-as-a-star instruments on board SoHO. We compare our results with other activity proxies.

  1. Self-assembly method for controlling spatial frequency response of plasmonic back reflectors in organic thin-film solar cells

    NASA Astrophysics Data System (ADS)

    Okamoto, Takayuki; Shinotsuka, Kei; Kawamukai, Etsuko; Ishibashi, Koji

    2017-01-01

    We propose a novel colloidal lithography technique that uses a mixture of colloidal particles with a few different diameters. This technique can be used for fabricating quasi-random nanostructures whose k-space spectra can be easily controlled by using an appropriate combination of particles. We introduced such nanostructures into the back reflectors of organic thin-film solar cells, where they serve as plasmonic back reflectors for recycling the nonabsorbed transmitted light into surface plasmons. The obtained photon-to-current efficiency was enhanced by 14-20% compared with that of a flat cell.

  2. Aspects of the Solar Tachocline

    NASA Technical Reports Server (NTRS)

    Elliott, J. R.

    1997-01-01

    The splitting of the frequencies of p-mode multiplets enables information to be gained about the internal rotation of the sun. Such data have revealed a transition at the base of the convection zone from differential rotation similar to that observed at the surface to almost solid-body rotation in the radiative interior. This transition region, known as the tachocline, has been found to be relatively narrow and centered below the base of the convection zone. In this paper, the evolution of the transition region is investigated numerically. Without a large anisotropic viscosity, the depth to which it would spread in one solar age, under the assumption of a constant prescribed differential rotation at the base of the convection zone, is found to be greater than its extent as inferred from helioseismology. In the second part of the paper a highly anisotropic turbulent viscosity with a large horizontal component, as suggested by Spiegel & Zahn (1992), is assumed. In this case, a steady tachocline is formed in which the advection of angular momentum balances the Reynolds stresses. The horizontal component of turbulent viscosity required to match the thickness of the tachocline to that obtained by helioseismology, is estimated to be 5 x 1O sq cm/s The transport of helium is studied in this case and is found to yield a sound-speed increase similar to that required by helioseismology.

  3. Explicit analytical modeling of the low frequency a-Si:H/c-Si heterojunction capacitance: Analysis and application to silicon heterojunction solar cells

    SciTech Connect

    Maslova, O.; Brézard-Oudot, A.; Gueunier-Farret, M.-E.; Alvarez, J.; Kleider, J.-P.

    2015-09-21

    We develop a fully analytical model in order to describe the temperature dependence of the low frequency capacitance of heterojunctions between hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si). We demonstrate that the slope of the capacitance-temperature (C-T) curve is strongly enhanced if the c-Si surface is under strong inversion conditions compared to the usually assumed depletion layer capacitance. We have extended our analytical model to integrate a very thin undoped (i) a-Si:H layer at the interface and the finite thickness of the doped a-Si:H layer that are used in high efficiency solar cells for the passivation of interface defects and to limit short circuit current losses. Finally, using our calculations, we analyze experimental data on high efficiency silicon heterojunction solar cells. The transition from the strong inversion limited behavior to the depletion layer behavior is discussed in terms of band offsets, density of states in a-Si:H, and work function of the indium tin oxide (ITO) front electrode. In particular, it is evidenced that strong inversion conditions prevail at the c-Si surface at high temperatures down to 250 K, which can only be reproduced if the ITO work function is larger than 4.7 eV.

  4. Effects of solar and geomagnetic activities on the sub-ionospheric very low frequency transmitter signals received by the DEMETER micro-satellite

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Yahia; Schwingenschuh, Konrad; Al-Haddad, Emad; Parrot, Michel; Galopeau, Patrick H. M.; Besser, Bruno; Stangl, Guenter; Voller, Wolfgang

    2012-04-01

    In the framework of seismic precursor electromagnetic investigations, we analyzed the very low frequency (VLF) amplitude signals recorded by the Instrument Champ Electrique (ICE) experiment on board the DEMETER micro-satellite. The sun-synchronous orbits of the micro-satellite allowed us to cover an invariant latitude of between -65° and +65° in a time interval of about 40 min. We considered four transmitter signals emitted by stations in Europe (France, FTU, 18.3 kHz; Germany, DFY, 16.58 kHz),Asia (Japan, JP, 17.8 kHz) and Australia (Australia, NWC, 19.8 kHz). We studied the variations of these VLF signals, taking into consideration: the signal-to-noise ratio, sunspots, and the geomagnetic activity. We show that the degree of correlation in periods of high geomagnetic and solar activities is, on average, about 40%. Such effects can be fully neglected in the period of weak activity. We also find that the solar activity can have a more important effect on the VLF transmitter signal than the geomagnetic activity. Our data are combined with models where the coupling between the lithosphere, atmosphere and ionosphere is essential to explain how ionospheric disturbances scatter the VLF transmitter signal.

  5. Design, Fabrication and Characterization of MIM Diodes and Frequency Selective Thermal Emitters for Solar Energy Harvesting and Detection Devices

    NASA Astrophysics Data System (ADS)

    Sharma, Saumya

    Energy harvesting using rectennas for infrared radiation continues to be a challenge due to the lack of fast switching diodes capable of rectification at THz frequencies. Metal insulator metal diodes which may be used at 30 THz must show adequate nonlinearity for small signal rectification such as 30 mV. In a rectenna assembly, the voltage signal received as an output from a single nanoantenna can be as small as ~30microV. Thus, only a hybrid array of nanoantennas can be sufficient to provide a signal in the ~30mV range for the diode to be able to rectify around 30THz. A metal-insulator-metal diode with highly nonlinear I-V characteristics is required in order for such small signal rectification to be possible. Such diode fabrication was found to be faced with two major fabrication challenges. The first one being the lack of a precisely controlled deposition process to allow a pinhole free insulator deposition less than 3nm in thickness. Another major challenge is the deposition of a top metal contact on the underlying insulating thin film. As a part of this research study, most of the MIM diodes were fabricated using Langmuir Blodgett monolayers deposited on a thin Ni film that was sputter coated on a silicon wafer. UV induced polymerization of the Langmuir Blodgett thin film was used to allow intermolecular crosslinking. A metal top contact was sputtered onto the underlying Langmuir Blodgett film assembly. In addition to material characterization of all the individual films using IR, UV-VIS spectroscopy, electron microscopy and atomic force microscopy, the I-V characteristics, resistance, current density, rectification ratio and responsivity with respect to the bias voltage were also measured for the electrical characterization of these MIM diodes. Further improvement in the diode rectification ratio and responsivity was obtained with Langmuir Blodgett films grown by the use of horizontally oriented organic molecules, due to a smaller tunneling distance that

  6. Actinometric measurement of j[O[sub 3]-O([sup 1]D)], the solar photolysis frequency of ozone to singlet D oxygen atoms

    SciTech Connect

    Tesfamariam, B.S.

    1992-01-01

    A chemical actinometer for measuring the solar photolysis frequency of ozone to [sup 1]D oxygen atoms, j[O[sub 3]-O([sup 1]D)], has been built. Ozone, generated by oxygen flowing through an electric discharge ozonizer, is mixed with helium and nitrous oxide. The mixture of gases passes through traps into an ozone meter and into a photolysis tube that can be exposed to sunlight. Sunlight in the wavelength region less than 320 nm, photolyzes ozone into oxygen molecules and excited oxygen atoms that are in [sup 1]D state. The [sup 1]D oxygen atoms formed react with N[sub 2]O and ozone to produce oxides of nitrogen. Computer model predictions show that NO[sub 2] is the major product. The gases after photolysis pass through an ozone removing trap into the detector. NO[sub 2] in the gas mixture is detected by its chemiluminescence reaction with luminol. The instrument is able to measure j[O[sub 3]-O([sup 1]D)] with a noise level less that 5 x 10[sup [minus]1] sec[sup [minus]1]. The instrument measures j[O[sub 3]-O([sup 1]D)] with a precision of [+-]10%. Sixty days of data are taken between February 19, 1991 and May 18, 1991 in Denver, Colorado. Over 400 clear day j[O[sub 3]-O(1D)] values are correlated with effective ozone column density. Seasonal variation of j[O[sub 3]-O([sup 1]D)] is calculated from the peak hourly average values near solar noon for the months February, March, April and May. j[O[sub 3]-O([sup 1]D)] increased by 34% from February to May. j[O[sub 3]-O([sup 1]D)] measured in this study is compared with previous measurements and model calculations. Three photometers with approximate cosine response have been built and compared to the j[O[sub 3]-O([sup 1]D)] actinometer. j[[sub 3]-O([sup 1]D)] values are also compared to an output of a radiometer that measures global solar radiation. A new method to estimate j[O[sub 3]-O([sup 1]D)] on cloudy days using the global solar radiation is successfully tested.

  7. Low-frequency observations of drifting, non-thermal continuum radio emission associated with the solar coronal mass ejections

    SciTech Connect

    Ramesh, R.; Kishore, P.; Barve, Indrajit V.; Kathiravan, C.; Mulay, Sargam M.; Wang, T. J.

    2013-11-20

    Low-frequency (80 MHz) imaging and spectral (≈85-20 MHz) observations of moving type IV radio bursts associated with coronal mass ejections (CMEs) from the Sun on three different days are reported. The estimated drift speed of the bursts is in the range ≈150-500 km s{sup –1}. We find that all three bursts are most likely due to second harmonic plasma emission from the enhanced electron density in the associated white-light CMEs. The derived maximum magnetic field strength of the latter is B ≈ 4 G at a radial distance of r ≈ 1.6 R {sub ☉}.

  8. High Efficiency Amorphous and Microcrystalline Silicon Based Double-Junction Solar Cells made with Very-High-Frequency Glow Discharge

    SciTech Connect

    Banerjee, Arindam

    2004-10-20

    We have achieved a total-area initial efficiency of 11.47% (active-area efficiency of 12.33%) on a-Si:H/μc-Si:H double-junction structure, where the intrinsic layer bottom cell was made in 50 minutes. On another device in which the bottom cell was made in 30 min, we achieved initial total-area efficiency of 10.58% (active-efficiency of 11.35%). We have shown that the phenomenon of ambient degradation of both μc-Si:H single-junction and a-Si:H/μc-Si:H double-junction cells can be attributed to impurity diffusion after deposition. Optimization of the plasma parameters led to alleviation of the ambient degradation. Appropriate current matching between the top and bottom component cells has resulted in a stable total-area efficiency of 9.7% (active-area efficiency of 10.42%) on an a-Si:H/μc-Si:H double-junction solar cell in which the deposition time for the μc-Si:H intrinsic layer deposition was of 30 min.

  9. Differential rotation in main-sequence solar-like stars: Qualitative inference from asteroseismic data

    SciTech Connect

    Lund, Mikkel N.; Christensen-Dalsgaard, Jørgen; Miesch, Mark S.

    2014-08-01

    Understanding differential rotation of Sun-like stars is of great importance for insight into the angular momentum transport in these stars. One means of gaining such information is that of asteroseismology. By a forward modeling approach we analyze in a qualitative manner the impact of different differential rotation profiles on the splittings of p-mode oscillation frequencies. The optimum modes for inference on differential rotation are identified along with the best value of the stellar inclination angle. We find that in general it is not likely that asteroseismology can be used to make an unambiguous distinction between a rotation profile such as a conical Sun-like profile and a cylindrical profile. In addition, it seems unlikely that asteroseismology of Sun-like stars will result in inferences on the radial profile of the differential rotation, such as can be done for red giants. At best, one could possibly obtain the sign of the radial differential rotation gradient. Measurements of the extent of the latitudinal differential from frequency splitting are, however, more promising. One very interesting aspect that could likely be tested from frequency splittings is whether the differential rotation is solar-like or anti-solar-like in nature, in the sense that a solar-like profile has an equator rotating faster than the poles.

  10. Observations of Low-degree Modes from the Solar Maximum Mission (extended Abstract)

    NASA Technical Reports Server (NTRS)

    Woodard, M.

    1984-01-01

    Mean frequencies, amplitudes, and linewidths for the solar 5 min p mode oscillations of degree 0, 1, and 2 have been obtained from approx. 280 days of SMM-ACRIM total irradiance data. The frequencies are in good agreement with measurements obtained from velocity data. The amplitudes of the modes lie along a well defined envelope of power vs. frequency, which peaks at 3.1 mHz and has a width of 0.7 mHz (FWHM). The r.m.s. amplitude of the highest peak in the spectrum (n=21, l=1) is approx. 3 ppm of the total flux. The linewidths of the narrowest l=O modes are approx. 1 micro Hz (FWHM). A broad continuum of power caused both by solar surface granulation and by instrumental noise interferes with the analysis of 5 min modes. The continuum spectral power in a 1 micro Hz band near 3 mHz corresponds to an apparent r.m.s. variation of approx. 0.5 parts per million of the mean solar flux.

  11. Solar and geomagnetic activity, extremely low frequency magnetic and electric fields and human health at the Earth's surface

    NASA Astrophysics Data System (ADS)

    Palmer, S. J.; Rycroft, M. J.; Cermack, M.

    2006-09-01

    The possibility that conditions on the Sun and in the Earth’s magnetosphere can affect human health at the Earth’s surface has been debated for many decades. This work reviews the research undertaken in the field of heliobiology, focusing on the effect of variations of geomagnetic activity on human cardiovascular health. Data from previous research are analysed for their statistical significance, resulting in support for some studies and the undermining of others. Three conclusions are that geomagnetic effects are more pronounced at higher magnetic latitudes, that extremely high as well as extremely low values of geomagnetic activity seem to have adverse health effects and that a subset of the population (10-15%) is predisposed to adverse health due to geomagnetic variations. The reported health effects of anthropogenic sources of electric and magnetic fields are also briefly discussed, as research performed in this area could help to explain the results from studies into natural electric and magnetic field interactions with the human body. Possible mechanisms by which variations in solar and geophysical parameters could affect human health are discussed and the most likely candidates investigated further. Direct effects of natural ELF electric and magnetic fields appear implausible; a mechanism involving some form of resonant absorption is more likely. The idea that the Schumann resonance signals could be the global environmental signal absorbed by the human body, thereby linking geomagnetic activity and human health is investigated. Suppression of melatonin secreted by the pineal gland, possibly via desynchronised biological rhythms, appears to be a promising contender linking geomagnetic activity and human health. There are indications that calcium ions in cells could play a role in one or more mechanisms. It is found to be unlikely that a single mechanism can explain all of the reported phenomena.

  12. The Transport of Low-frequency Turbulence in Astrophysical Flows. II. Solutions for the Super-Alfvénic Solar Wind

    NASA Astrophysics Data System (ADS)

    Adhikari, L.; Zank, G. P.; Bruno, R.; Telloni, D.; Hunana, P.; Dosch, A.; Marino, R.; Hu, Q.

    2015-05-01

    Zank et al. developed a turbulence transport model for low-frequency incompressible magnetohydrodynamic (MHD) turbulence in inhomogeneous flows in terms of the energy corresponding to forward and backward propagating modes, the residual energy, the correlation lengths corresponding to forward and backward propagating modes, and the correlation length of the residual energy. We apply the Zank et al. model to the super-Alfvénic solar wind i.e., |{\\boldsymbol{U}} |\\gg |{{{\\boldsymbol{V}} }A}| and solve the coupled equations for two cases, the first being the heliosphere from 0.29 to 5 AU with and without the Alfvén velocity, and the second being the “entire” heliosphere from 0.29 to 100 AU in the absence of the Alfvén velocity. The model shows that (1) shear driving is responsible for the in situ generation of backward propagating modes, (2) the inclusion of the background magnetic field modifies the transport of turbulence in the inner heliosphere, (3) the correlation lengths of forward and backward propagating modes are almost equal beyond ∼30 AU, and (4) the fluctuating magnetic and kinetic energies in MHD turbulence are in approximate equipartition beyond ∼30 AU. A comparison of the model results with observations for the two cases shows that the model reproduces the observations quite well from 0.29 to 5 AU. The outer heliosphere (\\gt 1 AU) observations are well described by the model. The temporal and latitudinal dependence of the observations makes a detailed comparison difficult but the overall trends are well captured by the models. We conclude that the results are a reasonable validation of the Zank et al. model for the super-Alfvénic solar wind.

  13. Five-minute oscillation power within magnetic elements in the solar atmosphere

    SciTech Connect

    Jain, Rekha; Gascoyne, Andrew; Hindman, Bradley W.; Greer, Benjamin

    2014-12-01

    It has long been known that magnetic plage and sunspots are regions in which the power of acoustic waves is reduced within the photospheric layers. Recent observations now suggest that this suppression of power extends into the low chromosphere and is also present in small magnetic elements far from active regions. In this paper we investigate the observed power suppression in plage and magnetic elements, by modeling each as a collection of vertically aligned magnetic fibrils and presuming that the velocity within each fibril is the response to buffeting by incident p modes in the surrounding field-free atmosphere. We restrict our attention to modeling observations made near the solar disk center, where the line-of-sight velocity is nearly vertical and hence, only the longitudinal component of the motion within the fibril contributes. Therefore, we only consider the excitation of axisymmetric sausage waves and ignore kink oscillations as their motions are primarily horizontal. We compare the vertical motion within the fibril with the vertical motion of the incident p mode by constructing the ratio of their powers. In agreement with observational measurements we find that the total power is suppressed within strong magnetic elements for frequencies below the acoustic cut-off frequency. However, further physical effects need to be examined for understanding the observed power ratios for stronger magnetic field strengths and higher frequencies. We also find that the magnitude of the power deficit increases with the height above the photosphere at which the measurement is made. Furthermore, we argue that the area of the solar disk over which the power suppression extends increases as a function of height.

  14. Five-minute Oscillation Power within Magnetic Elements in the Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Jain, Rekha; Gascoyne, Andrew; Hindman, Bradley W.; Greer, Benjamin

    2014-12-01

    It has long been known that magnetic plage and sunspots are regions in which the power of acoustic waves is reduced within the photospheric layers. Recent observations now suggest that this suppression of power extends into the low chromosphere and is also present in small magnetic elements far from active regions. In this paper we investigate the observed power suppression in plage and magnetic elements, by modeling each as a collection of vertically aligned magnetic fibrils and presuming that the velocity within each fibril is the response to buffeting by incident p modes in the surrounding field-free atmosphere. We restrict our attention to modeling observations made near the solar disk center, where the line-of-sight velocity is nearly vertical and hence, only the longitudinal component of the motion within the fibril contributes. Therefore, we only consider the excitation of axisymmetric sausage waves and ignore kink oscillations as their motions are primarily horizontal. We compare the vertical motion within the fibril with the vertical motion of the incident p mode by constructing the ratio of their powers. In agreement with observational measurements we find that the total power is suppressed within strong magnetic elements for frequencies below the acoustic cut-off frequency. However, further physical effects need to be examined for understanding the observed power ratios for stronger magnetic field strengths and higher frequencies. We also find that the magnitude of the power deficit increases with the height above the photosphere at which the measurement is made. Furthermore, we argue that the area of the solar disk over which the power suppression extends increases as a function of height.

  15. Stochastic excitation of the solar oscillations by turbulent convection

    NASA Astrophysics Data System (ADS)

    Willette, Gregory Thomas

    1994-01-01

    The thesis topic is the stochastic excitation of the solar p-modes by turbulent convection, and the work consists of four parts: three theoretical sections and one observational. In the first section of the thesis, an explicit calculation of the acoustic radiation of a buoyant oscillating bubble is presented as a model for the excitation of the solar p-modes. The central scientific issue addressed in this work is the cancellation of monopole and dipole radiation fields in an anisotropic medium, first pointed out by Goldreich and Kumar (1990). When the bubble oscillation frequency is small compared to the acoustic cutoff, the monopole and dipole disturbances cancel to the quadrupole order in the far field. The second section deals with the role of convective structures in a wide number of problems, including the creation of acoustic disturbances, the transport of heat and magnetic fields, and the penetration of flows into stable layers of the atmosphere (overshoot). A model of plume convection is developed to discuss these issues. It is argued that the scaleheight-sized flows (the only energetically significant ones) are properly characterized as coherent, entropy-preserving plumes, in contradistinction to the picture of amorphous parcels of fluid suggested by the Mixing Length Theory, and in spite of the large Reynolds numbers typical in astrophysical convection. The third section of the thesis is an analysis of high-resolution surface velocity data taken with a magneto-optical filter on the 10 inch telescope at Big Bear Solar Observatory. Estimates are obtained for the frequencies and amplitudes of the solar oscillations of high spherical harmonic degree (l approximately less than 2000). The observed mode energies follow a Boltzmann distribution (P(E) varies as exp(-E/(bar-E)), as is predicted in the stochastic excitation model. In the final section of the thesis, a derivation of the variational principle for an incompressible fluid is presented. The Lagrange and

  16. FREQUENCY OF SOLAR-LIKE SYSTEMS AND OF ICE AND GAS GIANTS BEYOND THE SNOW LINE FROM HIGH-MAGNIFICATION MICROLENSING EVENTS IN 2005-2008

    SciTech Connect

    Gould, A.; Dong, Subo; Gaudi, B. S.; Han, C. E-mail: gaudi@astronomy.ohio-state.ed

    2010-09-10

    suggests a universal separation distribution across 2 dex in planet-star separation, 2 dex in mass ratio, and 0.3 dex in host mass. Finally, if all planetary systems were 'analogs' of the solar system, our sample would have yielded 18.2 planets (11.4 'Jupiters', 6.4 'Saturns', 0.3 'Uranuses', 0.2 'Neptunes') including 6.1 systems with two or more planet detections. This compares to six planets including one two-planet system in the actual sample, implying a first estimate of 1/6 for the frequency of solar-like systems.

  17. Helioseismic Constraints on New Solar Models from the MoSEC Code

    NASA Technical Reports Server (NTRS)

    Elliott, J. R.

    1998-01-01

    Evolutionary solar models are computed using a new stellar evolution code, MOSEC (Modular Stellar Evolution Code). This code has been designed with carefully controlled truncation errors in order to achieve a precision which reflects the increasingly accurate determination of solar interior structure by helioseismology. A series of models is constructed to investigate the effects of the choice of equation of state (OPAL or MHD-E, the latter being a version of the MHD equation of state recalculated by the author), the inclusion of helium and heavy-element settling and diffusion, and the inclusion of a simple model of mixing associated with the solar tachocline. The neutrino flux predictions are discussed, while the sound speed of the computed models is compared to that of the sun via the latest inversion of SOI-NMI p-mode frequency data. The comparison between models calculated with the OPAL and MHD-E equations of state is particularly interesting because the MHD-E equation of state includes relativistic effects for the electrons, whereas neither MHD nor OPAL do. This has a significant effect on the sound speed of the computed model, worsening the agreement with the solar sound speed. Using the OPAL equation of state and including the settling and diffusion of helium and heavy elements produces agreement in sound speed with the helioseismic results to within about +.-0.2%; the inclusion of mixing slightly improves the agreement.

  18. Kepler Mission: a Discovery-Class Mission Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-Like Stars

    NASA Technical Reports Server (NTRS)

    Borucki, William; Koch, David; Lissauer, Jack; Basri, Gibor; Caldwell, John; Cochran, William; Dunham, Edward W.; Gilliland, Ronald; Caldwell, Douglas; Kondo, Yoji; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in the habitable zone (HZ). The Kepler Mission is designed around a 0.95 in aperture Schmidt-type telescope with an array of 42 CCDs designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. The photometer is scheduled to be launched into heliocentric orbit in 2007. Measurements of the depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. When combined with ground-based spectroscopy of these stars to fix the stellar parameters, the true planet radius and orbit scale, hence the position relative to the HZ are determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four year mission, hundreds of terrestrial planets should be discovered in and near the HZ of their stars if such planets are common. Extending the mission to six years doubles the expected number of Earth-size planets in the HZ. A null result would imply that terrestrial planets in the HZ occur in less than 1% of the stars and that life might be quite rare. Based on the results of the current Doppler-velocity discoveries, detection of a thousand giant planets is expected. Information on their albedos and densities of those giants showing transits will be obtained.

  19. Kepler Mission: A Wide-FOV Photometer Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-like stars

    NASA Technical Reports Server (NTRS)

    Borucki, William; Koch, David; Lissauer, Jack; Basri, Gibor; Caldwell, John; Cochran, William; Dunham, Edward W.; Gilliland, Ronald; Jenkins, Jon M.; Caldwell, Douglas; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in the habitable zone (HZ). The Kepler Mission is designed around a 0.95 m aperture Schmidt-type telescope with an array of 42 CCDs designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. The photometer is scheduled to be launched into heliocentric orbit in 2007. Measurements of the depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. When combined with ground-based spectroscopy of these stars to fix the stellar parameters, the true planet radius and orbit scale, hence the position relative to the HZ are determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four year mission, hundreds of terrestrial planets should be discovered in and near the HZ of their stars if such planets are common. A null result would imply that terrestrial planets in the HZ occur in less than 1% of the stars and that life might be quite rare. Based on the results of the current doppler-velocity discoveries, detection of a thousand giant planets is expected. Information on their albedos and densities of those giants showing transits will be obtained.

  20. Cyclic thermal signature in a global MHD simulation of solar convection

    NASA Astrophysics Data System (ADS)

    Cossette, J.; Charbonneau, P.; Smolarkiewicz, P. K.

    2013-12-01

    Space-based observations have clearly established that total solar irradiance (TSI) varies on time scales from minutes to days and months as well as on the longer time scale of the 11-year solar cycle. The most conspicuous of these variations is arguably the slight increase of TSI (0.1%) at solar maxima relative to solar minima. Models that include contributions from surface solar magnetism alone (i.e. sunspots, faculae and magnetic network) have been very successful at reproducing the observed TSI fluctuations on time scales shorter than a year, but leave some doubts as to the origin of the longer decadal fluctuations. In particular, one school of thought argues that surface magnetism alone can explain the entire TSI variance; see (Lean & al. 1998, ApJ, 492, 390), whereas; the other emphasizes on taking into account the effect of a global modulation of solar thermal structure by magnetic activity; see (Li & al. 2003, ApJ, 591, 1267). Observationally, the potential for the occurrence of magnetically-modulated global structural changes is supported by a positive correlation between p-mode oscillation frequencies and the TSI cycle as well as by recent evidence for a long-term trend in the TSI record that is not seen in indicators of surface magnetism; see (Bhatnagar & al. 1999, ApJ, 521, 885; Fröhlich 2013, Space Sci Rev,176, 237). Additionally, 1D structural solar models have demonstrated that the inclusion of a magnetically-modulated turbulent mechanism could explain the observed p-mode oscillation frequency changes with great accuracy. However, these models relied upon an ad-hoc parametrization of the alleged process and therefore obtaining a complete physical picture of the modulating mechanism requires solving the equations governing the self-consistent evolution of the solar plasma. Here we present a global magnetohydrodynamical (MHD) simulation of solar convection extending over more than a millennium that produces large-scale solar-like axisymmetric magnetic

  1. Solar collection

    NASA Astrophysics Data System (ADS)

    Cole, S. I.

    1984-08-01

    Solar dishes, photovoltaics, passive solar building and solar hot water systems, Trombe walls, hot air panels, hybrid solar heating systems, solar grain dryers, solar greenhouses, solar hot water worhshops, and solar workshops are discussed. These solar technologies are applied to residential situations.

  2. Note on one-fluid modeling of low-frequency Alfvénic fluctuations in a solar wind plasma with multi-ion components

    SciTech Connect

    Nariyuki, Y.; Umeda, T.; Suzuki, T. K.; Hada, T.

    2015-12-15

    A simple point of view that non-zero Alfvén ratio (residual energy) appears as a consequence of one-fluid modeling of uni-directional Alfvén waves in a solar wind plasma is presented. Since relative speeds among ions are incorporated into the one-fluid model as a pressure anisotropy, the Alfvén ratio can be finite due to the decrease in the phase velocity. It is shown that a proton beam component typically found in the solar wind plasma can contribute to generating non-zero Alfvén ratio observed in the solar wind plasma. Local equilibrium velocity distribution functions of each ion component are also discussed by using maximum entropy principle.

  3. Simultaneous observations of solar sporadic radio emission by the radio telescopes UTR-2, URAN-2 and NDA within the frequency range 8-42 MHz

    NASA Astrophysics Data System (ADS)

    Melnik, V.; Konovalenko, A.; Brazhenko, A.; Briand, C.; Dorovskyy, V.; Zarka, P.; Denis, L.; Bulatzen, V.; Frantzusenko, A.; Rucker, H.; Stanislavskyy, A.

    2012-09-01

    From 25 June till 12 August 2011 sporadic solar radio emission was observed simultaneously by three separate radio telescopes: UTR-2 (Kharkov, Ukraine), URAN-2 (Poltava, Ukraine) and NDA (Nancay, France). During these observations some interesting phenomena were observed. Some of them are discussed in this paper.

  4. Asteroseismic Tools and Analysis of Solar-like Oscillations in Archival Kepler Data

    NASA Astrophysics Data System (ADS)

    Metcalfe, Travis

    While the Kepler mission's main goal consists of searching for exoplanets through the detection of transits, asteroseismic analysis of the light curves is also possible thanks to the excellent quality of the data. The 150,000 stars, for which at least 7 months of data have been made public, contain ~10% red giants and ~1% solar-type stars. The long- cadence data on red giants and short cadence data on solar-type stars allow us to detect their solar-like oscillations. With the acoustic p-mode parameters, we can estimate the mass and radius of the star either with scaling relations or by using a stellar evolution code [e.g. the Asteroseismic Modeling Portal (AMP, http://amp.ucar.edu/) developed at HAO]. Our study will include stars that host an exoplanet candidate. The determination of the stellar properties will allow us to better constrain the stellar and planetary evolution and we will investigate the distribution of the properties of these particular stars. The goal of this proposal is to provide community tools for asteroseismology and produce a catalog of data products by applying these tools to Kepler public data. The data produced by the Kepler science team is optimized to search for exoplanets, but some of the stellar information at low frequency can be filtered out. Scientists from the Kepler Asteroseismic Science Consortium (KASC) developed their own software (Garcia et al. 2011) to correct the data for instrumental effects while keeping as much information as possible at low frequency. We will improve and automate this software and apply it to the Kepler public data in collaboration with the Kepler Guest Observer office. The corrected data will be archived in an online database, as a section of the AMP website. To analyze the large quantity of data provided by Kepler, we have also developed a pipeline (A2Z, Mathur et al. 2010) that retrieves asteroseismic parameters and that has been extensively tested, validated, and used within the KASC. We will apply A

  5. Nearly-uniform internal rotation of solar-like main sequence stars revealed by asteroseismology and spectroscopic measurements

    NASA Astrophysics Data System (ADS)

    Benomar, Othman Michel; Takata, Masao; Shibahashi, Hiromoto; Ceillier, Tugdual; Garcia, Rafael

    2015-08-01

    Stellar pulsations, which can be trapped acoustic waves (p modes), internal gravity waves (g modes) or a mixture of two, have frequencies that depend on the properties of the stellar interior, such as the internal rotation.Helioseismology extensively exploited these pulsations and, by the means of seismic inversion, has revealed a nearly uniform rotation profile, with variations that do not exceed 30% in the radial direction (e.g. Thompson et al. 2003). To conciliate models with observations, an efficient mechanism of transport of angular momentum from the core to the envelope is required.The necessity of an efficient angular momentum transport was also revealed on two main-sequence stars showing p modes and g modes (Kurtz et al. 2014, Saio et al. 2015) and on several evolved stars solar-like showing mixed modes (Deheuvels et al. 2012, 2014).However, the number of stars with a measured internal rotation structure is still limited. For low-mass main-sequence stars showing solar-like oscillations, the measure of the internal rotation profile is limited because only the low degree p modes can be observed by unresolved photometry.Yet, by comparing the average surface rotation with the average of the internal rotation, it is possible to evaluate the degree of differential rotation between deep layers and the surface. The surface rotation can be derived by spectroscopic vsin(i) or by the periodic luminosity variation due to surface spots, while the average internal rotation is determined by asteroseismology, using the so-called rotational splitting.We performed this comparison on 22 solar-like stars of the main sequence. We show that the rotation at the surface and in the interior are generally close to each other. For 10 stars, the difference is clearly too small to be explained by simple evolutionary models that assume local conservation of angular momentum. Furthermore, by adopting a simple two-zone model, we show that 20 out of the 22 stars have a rotation rate in

  6. Standard solar models, with and without helium diffusion, and the solar neutrino problem

    NASA Astrophysics Data System (ADS)

    Bahcall, J. N.; Pinsonneault, M. H.

    1992-10-01

    effects of helium diffusion and the other improvements in the description of the solar interior that are implemented in this paper, the inferred primordial solar helium abundance is Y=0.273. The calculated depth of the convective zone is R=0.707Rsolar, in agreement with the value of 0.713Rsolar inferred by Christensen-Dalsgaard, Gough, and Thompson from a recent analysis of the observed p-mode oscillation frequencies. Including helium diffusion increases the calculated present-day hydrogen surface abundance by about 4%, decreases the helium abundance by approximately 11%, and increases the calculated heavy-element abundance by about 4%. In the Appendix, we present detailed numerical tables of our best standard solar models computed both with and without including helium diffusion. In the context of the MSW (Mikheyev-Smirnov-Wolfenstein) or other weak-interaction solutions of the solar neutrino problem, the numerical models can be used to compute the influence of the matter in the sun on the observed neutrino fluxes.

  7. The analysis of solar models: Neutrinos and oscillations

    NASA Technical Reports Server (NTRS)

    Ulrich, R. K.; Rhodes, E. J., Jr.; Tomczyk, S.; Dumont, P. J.; Brunish, W. M.

    1983-01-01

    Tests of solar neutrino flux and solar oscillation frequencies were used to assess standard stellar structure theory. Standard and non-standard solar models are enumerated and discussed. The field of solar seismology, wherein the solar interior is studied from the measurement of solar oscillations, is introduced.

  8. Uncertainties for two-dimensional models of solar rotation from helioseismic eigenfrequency splitting

    NASA Technical Reports Server (NTRS)

    Genovese, Christopher R.; Stark, Philip B.; Thompson, Michael J.

    1995-01-01

    Observed solar p-mode frequency splittings can be used to estimate angular velocity as a function of position in the solar interior. Formal uncertainties of such estimates depend on the method of estimation (e.g., least-squares), the distribution of errors in the observations, and the parameterization imposed on the angular velocity. We obtain lower bounds on the uncertainties that do not depend on the method of estimation; the bounds depend on an assumed parameterization, but the fact that they are lower bounds for the 'true' uncertainty does not. Ninety-five percent confidence intervals for estimates of the angular velocity from 1986 Big Bear Solar Observatory (BBSO) data, based on a 3659 element tensor-product cubic-spline parameterization, are everywhere wider than 120 nHz, and exceed 60,000 nHz near the core. When compared with estimates of the solar rotation, these bounds reveal that useful inferences based on pointwise estimates of the angular velocity using 1986 BBSO splitting data are not feasible over most of the Sun's volume. The discouraging size of the uncertainties is due principally to the fact that helioseismic measurements are insensitive to changes in the angular velocity at individual points, so estimates of point values based on splittings are extremely uncertain. Functionals that measure distributed 'smooth' properties are, in general, better constrained than estimates of the rotation at a point. For example, the uncertainties in estimated differences of average rotation between adjacent blocks of about 0.001 solar volumes across the base of the convective zone are much smaller, and one of several estimated differences we compute appears significant at the 95% level.

  9. Solar astronomy

    NASA Technical Reports Server (NTRS)

    Rosner, Robert; Noyes, Robert; Antiochos, Spiro K.; Canfield, Richard C.; Chupp, Edward L.; Deming, Drake; Doschek, George A.; Dulk, George A.; Foukal, Peter V.; Gilliland, Ronald L.

    1991-01-01

    An overview is given of modern solar physics. Topics covered include the solar interior, the solar surface, the solar atmosphere, the Large Earth-based Solar Telescope (LEST), the Orbiting Solar Laboratory, the High Energy Solar Physics mission, the Space Exploration Initiative, solar-terrestrial physics, and adaptive optics. Policy and related programmatic recommendations are given for university research and education, facilitating solar research, and integrated support for solar research.

  10. Fabrication of P-Type ZnO:N Film by Radio-Frequency Magnetron Sputtering for Extremely Thin Absorber Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Wang, Xiang-Hu; Li, Rong-Bin; Fan, Dong-Hua

    2013-03-01

    We successfully fabricate p-type ZnO:N films by using rf magnetron sputtering and in situ annealing in O2 atmosphere. These p-type ZnO:N films can be used as p-type window materials for extremely thin absorber (ETA) solar cells composed of quartz glass/p-ZnO:N/i-ZnO/CdSe/i-ZnO/n-ZnO:Al. The short-circuit photocurrent density, open circuit voltage, fill factor and conversion efficiency of the ETA solar cells can be determined to be 8.549 mA/cm2, 0.702V, 0.437 and 2.623%, respectively, through measurements of photovoltaic properties under illumination with a 100mW/cm2 at air-mass (AM) 1.5.

  11. The normal modes of a resonant cavity containing discrete inhomogeneities - The influence of fibril magnetic fields on the solar acoustic oscillations

    NASA Technical Reports Server (NTRS)

    Bogdan, Thomas J.; Cattaneo, Fausto

    1989-01-01

    Motivated by considerations of the interaction between fibril magnetic fields and solar p-modes, the acoustic spectrum of a cylindrical cavity filled with ideal gas in which a number of magnetic flux tubes are embedded is studied. A formalism, based on the T-matrix approach to acoustic scattering, is developed which can be used to determine the eigenfrequencies and eigenfunctions for any arbitrary distribution of flux tubes. For weak scatterers, the frequency shifts and velocity eigenfunctions are calculated using perturbation theory for the cases of a single flux tube and a random distribution of up to 100 flux tubes. The results of this 'exact' approach are used to give a critical appraisal of the predictions of theories based on some form of averaging, such as the one discussed recently by Bogdan and Zweibel (1987).

  12. Simultaneous observations of solar sporadic radio emission by the radio telescopes UTR-2, URAN-2 and NDA within the frequency range 8-41MHz

    NASA Astrophysics Data System (ADS)

    Melnik, V. N.; Konovalenko, A. A.; Rucker, H. O.; Brazhenko, A. I.; Briand, C.; Dorovskyy, V. V.; Zarka, P.; Denis, L.; Bulatzen, V. G.; Frantzusenko, A. V.; Stanislavskyy, A. A.

    2012-04-01

    From 25 June till 12 August 2011 sporadic solar radio emission was observed simultaneously by three separate radio telescopes: UTR-2 (Kharkov, Ukraine), URAN-2 (Poltava, Ukraine) and NDA (Nancay, France). During these observations several type II bursts with double and triple harmonics were registered, as well as type II bursts with complex herringbone structure. The events of particular interest were type II bursts registered on 9 and 11 August 2011. These bursts had opposite sign of circular polarization at different parts of their dynamic spectra. In our opinion we registered the emissions, which came from the different parts of the shock propagating through the solar corona. We have observed also groups of type III bursts merged into one burst, type III bursts with triple harmonics and type III bursts with "split" polarization. In addition some unusual solar bursts were registered: storms of strange narrow-band (up to 500kHz) bursts with high polarization degree (about 80%), decameter spikes of extremely short durations (200-300ms), "tadpole-like" bursts with durations of 1-2s and polarization degree up to 60%.

  13. Solar Oscillations

    NASA Technical Reports Server (NTRS)

    Duvall, Thomas

    2004-01-01

    Oscillations were first detected in the solar photosphere in 1962 by Leighton and students. In 1970 it was calculated that these oscillations, with a period near five minutes, were the manifestations of acoustic waves trapped in the interior. The subsequent measurements of the frequencies of global oscillation modes from the spatio-temporal power spectrum of the waves made possible the refinement of solar interior models. Over the years, increased understanding of the nuclear reaction rates, the opacity, the equation of state, convection, and gravitational settling have resulted. Mass flows shift the frequencies of modes leading to very accurate measurements of the interior rotation as a function of radius and latitude. In recent years, analogues of terrestrial seismology have led to a tomography of the interior, including measurements of global north-south flows and flow and wave speed measurements below features such as sunspots. The future of helioseismology seems bright with the approval of NASA's Solar Dynamics Observatory mission, to be launched in 2008.

  14. Corruption of radio metric Doppler due to solar plasma dynamics: S/X dual-frequency Doppler calibration for these effects

    NASA Technical Reports Server (NTRS)

    Winn, F. B.; Reinbold, S. R.; Yip, K. W.; Koch, R. E.; Lubeley, A.

    1975-01-01

    Doppler data from Mariner 6, 7, 9, and 10 and Pioneer 10 and 11 were discussed and the rms noise level for various sun-earth-probe angles were shown. The noise levels of both S- and X-band Doppler data for sun-earth-probe angles smaller than 20 deg were observed to be orders of magnitude greater than nominal. Such solar plasma-related Doppler degradation reduced the Mariner 10-Mercury 11 encounter navigation accuracy by nearly a factor of 10. Furthermore, this degradation was shown to be indirectly related to plasma dynamics and not a direct measure of the dynamics.

  15. Scintillation effects on radio wave propagation through solar corona

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Sue, M. K.; Bedrossian, A.; Sniffin, R. W.

    2002-01-01

    When RF waves pass through the solar corona and solar wind regions close to the Sun, strong scintillation effects appear at their amplitude, frequency and phase, especially in the regions very close to the Sun (less than 4 solar radius).

  16. Optoelectronic transport properties in amorphous/crystalline silicon solar cell heterojunctions measured by frequency-domain photocarrier radiometry: Multi-parameter measurement reliability and precision studies

    SciTech Connect

    Zhang, Y.; Melnikov, A.; Mandelis, A.; Halliop, B.; Kherani, N. P.; Zhu, R.

    2015-03-15

    A theoretical one-dimensional two-layer linear photocarrier radiometry (PCR) model including the presence of effective interface carrier traps was used to evaluate the transport parameters of p-type hydrogenated amorphous silicon (a-Si:H) and n-type crystalline silicon (c-Si) passivated by an intrinsic hydrogenated amorphous silicon (i-layer) nanolayer. Several crystalline Si heterojunction structures were examined to investigate the influence of the i-layer thickness and the doping concentration of the a-Si:H layer. The experimental data of a series of heterojunction structures with intrinsic thin layers were fitted to PCR theory to gain insight into the transport properties of these devices. The quantitative multi-parameter results were studied with regard to measurement reliability (uniqueness) and precision using two independent computational best-fit programs. The considerable influence on the transport properties of the entire structure of two key parameters that can limit the performance of amorphous thin film solar cells, namely, the doping concentration of the a-Si:H layer and the i-layer thickness was demonstrated. It was shown that PCR can be applied to the non-destructive characterization of a-Si:H/c-Si heterojunction solar cells yielding reliable measurements of the key parameters.

  17. Solar Power Satellite (SPS) pilot beam and communication link subsystem investigation study, phase 1. [ionospheric propagation, radio frequency interference, and microwave transmission

    NASA Technical Reports Server (NTRS)

    1979-01-01

    A preliminary engineering model of ionospheric interactions with the pilot beam was established and used to demonstrate that the dual frequency baseline pilot beam system might not be viable in the presence of an unstable transmission path. Alternate approaches to remove this difficulty are described. Although ionospheric fluctuations will not significantly degrade beam pointing or raise the sidelobe levels, they will reduce transmission efficiency by upwards of 25%. Mitigating strategies to substantially reduce this effect are proposed. Based on the Klystron noise spectrum, the pilot beam transmitter power was determined as a function of frequency offset from the power beam carrier frequency. The RFI from the pilot beam, on the ground and at geosynchronous orbit is shown. Noise levels on the earth's surface due to the SPS are presented as a function of frequency and the number of SPS systems. Analysis of the communication subsystem indicates that a standard telemetry line of 1.544 MB/s would satisfy both voice and data link requirements. Additional links would be required for TV and radio transmissions.

  18. Photocharge transport and recombination measurements in amorphous silicon films and solar cells by photoconductive frequency mixing: Annual subcontract report, 20 April 1998--19 April 1999

    SciTech Connect

    Braunstein, R.; Kattwinkel, A.; Liebe, J.; Sun, G.

    2000-02-28

    In the present phase of the program, the transport parameters of a number of amorphous semiconductors prepared by a number of techniques were determined by the photoconductive frequency mixing technique. This technique enabled the authors to determine the drift mobility, md, and the photomixing lifetime, t. The technique is based on the idea of heterodyne detection for photoconductors. When two similarly polarized monochromatic optical beams of slightly different frequencies are incident upon a photoconductor, the generation rate of electron-hole pairs will produce a photocurrent, when a dc-bias is applied, which will contain components resulting from the square of the sum of the individual incident fields. Consequently, a photocurrent will be produced, which will consist of a direct current and a microwave current corresponding to the beat frequency. These two currents allow a separate determination of the drift mobility and the photomixing lifetime of the photogenerated carriers. In the present work, the longitudinal modes of a He-Ne laser were employed to generate a beat frequency of 252 MHz; all the measurements were performed at this frequency for the data indicated in the accompanying figures. The following topics were explored: Measurements of the charge transport parameters of homogeneous a-SiGe:H alloys produced by NREL employing the hot-wire technique; The change in the charge transport parameters in the transition from hydrogenated amorphous silicon to microcrystalline silicon for material produced by NREL and MVSystems; The improvement in instrumentation of the photomixing measurements; Measurements of the hydrostatic dependency of the transport parameters of amorphous silicon; and Preliminary photomixing measurements on p-i-n devices.

  19. Effects of pulsed sputtering frequency on the uniformity of Al:ZnO's transparent conductive oxide properties for solar cell applications

    SciTech Connect

    Yang, Wonkyun; Joo, Junghoon

    2009-11-15

    Bipolar pulsed magnetron sputtering is used to deposit Al doped ZnO (AZO) on a glass substrate for a transparent conducting oxide in a solar cell structure. A 5x25 in.{sup 2} AZO target was sputtered by 50-250 kHz bipolar pulsed dc power supply to deposit a 400x400 mm{sup 2} area by swinging back and forth. Sheet resistance, surface morphology, and optical transmittance were measured at different positions on 16 witness samples (small glass slides) to evaluate uniformity. In the thickness of 800 nm, the average value of sheet resistance was 30 {Omega}/{open_square} and the average resistivity was 2.1x10{sup -3} {Omega} cm. Transmittance was 50%-80% over the visible range. The nonuniformities of thickness, transmittance, and resistivity in the 400x400 mm{sup 2} area were 5.8%, 0.8%, and within 9.5%, respectively.

  20. Frequency up-conversion in nonpolar a-plane GaN/AlGaN based multiple quantum wells optimized for applications with silicon solar cells

    SciTech Connect

    Radosavljević, S.; Radovanović, J. Milanović, V.; Tomić, S.

    2014-07-21

    We have described a method for structural parameters optimization of GaN/AlGaN multiple quantum well based up-converter for silicon solar cells. It involves a systematic tuning of individual step quantum wells by use of the genetic algorithm for global optimization. In quantum well structures, the up-conversion process can be achieved by utilizing nonlinear optical effects based on intersubband transitions. Both single and double step quantum wells have been tested in order to maximize the second order susceptibility derived from the density matrix formalism. The results obtained for single step wells proved slightly better and have been further pursued to obtain a more complex design, optimized for conversion of an entire range of incident photon energies.

  1. g-modes and the solar neutrino problem

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Kumar, Pawan

    1993-01-01

    We show that low-order g-modes with large enough amplitudes to affect significantly the solar neutrino fluxes would produce surface velocities that are 10 exp 4 times larger than the observed upper limits and hence are ruled out by existing data. We also demonstrate that any large-amplitude, short-period oscillations that grow on a Kelvin-Helmholtz time scale will require, to affect solar neutrino fluxes, a large amount of energy (for g-modes, 10 exp 9 times the energy in the observed p-mode oscillations) and a tiny amount of dissipation (for g modes, 10 exp -8 the fractional dissipation rate of the p-modes).

  2. The Solar-Stellar Connection: Magneto-Acoustic Pulsations in 1.5 M ⊙ 2 M ⊙ Peculiar A Stars

    NASA Astrophysics Data System (ADS)

    Kurtz, D. W.

    2008-09-01

    Stellar astronomers look on in envy at the wealth of data, the incredible spatial resolution, and the maturity of the theoretical understanding of the Sun. Yet the Sun is but one star, so stellar astronomy is of great interest to solar astronomers for its range of different conditions under which to test theoretical understanding gained from the study of the Sun. The rapidly oscillating peculiar A stars are of particular interest to solar astronomers. They have strong, global, dipolar magnetic fields with strengths in the range 1 25 kG, and they pulsate in high-overtone p modes similar to those in the Sun; thus they offer a unique opportunity to study the interaction of pulsation, convection, and strong magnetic fields, as is now done in the local helioseismology of sunspots. Some of them even pulsate in modes with frequencies above the acoustic cutoff frequency, in analogy with the highest frequency solar modes, but with mode lifetimes up to decades in the roAp stars, very unlike the short mode lifetimes of the Sun. They offer the most extreme cases of atomic diffusion, a small, but important ingredient of the standard solar model with wide application in stellar astrophysics. They are compositionally stratified and are observed and modelled as a function of atmospheric depth and thus can inform plans to expand helioseismic observations to have atmospheric depth resolution. Study of this unique class of pulsating stars follows the advanced state of studies of the Sun and offers more extreme conditions for the understanding of physics shared with the Sun.

  3. The Galileo solar redshift experiment

    NASA Astrophysics Data System (ADS)

    Krisher, Timothy P.; Morabito, David D.; Anderson, John D.

    1993-04-01

    From the October 1989 launch to the first December 1990 earth gravity assist, we regularly obtained frequency measurements of the spacecraft clock - an ultrastable crystal oscillator (USO) supplied by Frequency Electronics, Inc. The solar gravitational redshift in frequency was readily detectable, and because of the unique variations in heliocentric distance we could separate the general relativistic effects from the USO's intrinsic frequency variations. We have verified the total frequency shift predicted by general relativity to 0.5 percent accuracy, and the solar gravitational redshift to 1 percent accuracy.

  4. Beat frequency interference pattern characteristics study

    NASA Technical Reports Server (NTRS)

    Ott, J. H.; Rice, J. S.

    1981-01-01

    The frequency spectra and corresponding beat frequencies created by the relative motions between multiple Solar Power Satellites due to solar wind, lunar gravity, etc. were analyzed. The results were derived mathematically and verified through computer simulation. Frequency spectra plots were computer generated. Detailed computations were made for the seven following locations in the continental US: Houston, Tx.; Seattle, Wa.; Miami, Fl.; Chicago, Il.; New York, NY; Los Angeles, Ca.; and Barberton, Oh.

  5. Effects of heavy-element settling on solar neutrino fluxes and interior structure

    NASA Technical Reports Server (NTRS)

    Proffitt, Charles R.

    1994-01-01

    We consider the effects of gravitational settling of both He and heavier elements on the predicted solar neutrino fluxes and interior sound speed and density profiles. We find that while the structural changes that result from the inclusion of both He and heavy-element settling are only slightly larger than the changes resulting from the inclusion of He settling alone, the additional increases in expected neutrino fluxes are of comparable size. Our preferred model with both He and heavy-element settling has neutrino count rates of 9.0 SNU for Cl-37 detectors and 137 SNU for Ga-71 detectors, as compared to 7.1 and 127 SNU for a comparable model without any diffusive separation, or 8.0 and 132 SNU for a model that includes He settling alone. We suggest that the correction factors by which the predicted neutrino fluxes of solar models calculated without including the effects of diffusion should be multiplied are 1.25 +/- 0.08 for Cl detectors, 1.07 +/- 0.02 for Ga detectors, and 1.28 +/- 0.09 for the B-8 flux (1 sigma errors). Comparison of internal sound speed and density profiles strongly suggests that the additional changes in calculated p-mode oscillation frequencies due to the inclusion of heavy-element settling will be small compared to the changes that result from He settling alone, especially for the higher degree modes. All models with diffusive separation give much better agreement with the observed depth of the convection zone than do nondiffusive models. The model that includes both He and heavy-element settling requires an initial He mass fraction Y = 0.280 and has a surface He abundance of Y = 0.251 at the solar age.

  6. Mars solar conjunction prediction modeling

    NASA Astrophysics Data System (ADS)

    Srivastava, Vineet K.; Kumar, Jai; Kulshrestha, Shivali; Kushvah, Badam Singh

    2016-01-01

    During the Mars solar conjunction, telecommunication and tracking between the spacecraft and the Earth degrades significantly. The radio signal degradation depends on the angular separation between the Sun, Earth and probe (SEP), the signal frequency band and the solar activity. All radiometric tracking data types display increased noise and signatures for smaller SEP angles. Due to scintillation, telemetry frame errors increase significantly when solar elongation becomes small enough. This degradation in telemetry data return starts at solar elongation angles of around 5° at S-band, around 2° at X-band and about 1° at Ka-band. This paper presents a mathematical model for predicting Mars superior solar conjunction for any Mars orbiting spacecraft. The described model is simulated for the Mars Orbiter Mission which experienced Mars solar conjunction during May-July 2015. Such a model may be useful to flight projects and design engineers in the planning of Mars solar conjunction operational scenarios.

  7. Low Frequency Radio Experiment (LORE)

    NASA Astrophysics Data System (ADS)

    Manoharan, P. K.; Naidu, Arun; Joshi, B. C.; Roy, Jayashree; Kate, G.; Pethe, Kaiwalya; Galande, Shridhar; Jamadar, Sachin; Mahajan, S. P.; Patil, R. A.

    2016-03-01

    In this paper, we present a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii, i.e., at frequencies below 30 MHz. The LORE can be complimentary to the planned Indian solar mission, “Aditya-L1” and its other payloads as well as synergistic to ground-based interplanetary scintillation (IPS) observations, which are routinely carried out by the Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and its particular suitability for providing measurements on the detailed time and frequency structure of fast drifting type-III and slow drifting type-II radio bursts with unprecedented time and frequency resolutions. We also brief the gonio-polarimetry, which is possible with better-designed antennas and state-of-the-art electronics, employing FPGAs and an intelligent data management system. These would enable us to make a wide range of studies, such as nonlinear plasma processes in the Sun-Earth distance, in-situ radio emission from coronal mass ejections (CMEs), interplanetary CME driven shocks, nature of ICMEs driving decelerating IP shocks and space weather effects of solar wind interaction regions.

  8. Solar Energy.

    ERIC Educational Resources Information Center

    Eaton, William W.

    Presented is the utilization of solar radiation as an energy resource principally for the production of electricity. Included are discussions of solar thermal conversion, photovoltic conversion, wind energy, and energy from ocean temperature differences. Future solar energy plans, the role of solar energy in plant and fossil fuel production, and…

  9. Solar energy

    NASA Technical Reports Server (NTRS)

    Rapp, D.

    1981-01-01

    The book opens with a review of the patterns of energy use and resources in the United States, and an exploration of the potential of solar energy to supply some of this energy in the future. This is followed by background material on solar geometry, solar intensities, flat plate collectors, and economics. Detailed attention is then given to a variety of solar units and systems, including domestic hot water systems, space heating systems, solar-assisted heat pumps, intermediate temperature collectors, space heating/cooling systems, concentrating collectors for high temperatures, storage systems, and solar total energy systems. Finally, rights to solar access are discussed.

  10. Solar Systems

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The solar collectors shown are elements of domestic solar hot water systems produced by Solar One Ltd., Virginia Beach, Virginia. Design of these systems benefited from technical expertise provided Solar One by NASA's Langley Research Center. The company obtained a NASA technical support package describing the d e sign and operation of solar heating equipment in NASA's Tech House, a demonstration project in which aerospace and commercial building technology are combined in an energy- efficient home. Solar One received further assistance through personal contact with Langley solar experts. The company reports that the technical information provided by NASA influenced Solar One's panel design, its selection of a long-life panel coating which increases solar collection efficiency, and the method adopted for protecting solar collectors from freezing conditions.

  11. Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hänsch, Theodor W.; Picqué, Nathalie

    Much of modern research in the field of atomic, molecular, and optical science relies on lasers, which were invented some 50 years ago and perfected in five decades of intense research and development. Today, lasers and photonic technologies impact most fields of science and they have become indispensible in our daily lives. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. Through the development of optical frequency comb techniques, technique a setup of the size 1 ×1 m2, good for precision measurements of any frequency, and even commercially available, has replaced the elaborate previous frequency-chain schemes for optical frequency measurements, which only worked for selected frequencies. A true revolution in optical frequency measurements has occurred, paving the way for the creation of all-optical clocks clock with a precision that might approach 10-18. A decade later, frequency combs are now common equipment in all frequency metrology-oriented laboratories. They are also becoming enabling tools for an increasing number of applications, from the calibration of astronomical spectrographs to molecular spectroscopy. This chapter first describes the principle of an optical frequency comb synthesizer. Some of the key technologies to generate such a frequency comb are then presented. Finally, a non-exhaustive overview of the growing applications is given.

  12. Solar chromospheric spicules from the leakage of photospheric oscillations and flows.

    PubMed

    De Pontieu, Bart; Erdélyi, Robert; James, Stewart P

    2004-07-29

    Spicules are dynamic jets propelled upwards (at speeds of approximately 20 km s(-1)) from the solar 'surface' (photosphere) into the magnetized low atmosphere of the Sun. They carry a mass flux of 100 times that of the solar wind into the low solar corona. With diameters close to observational limits (< 500 km), spicules have been largely unexplained since their discovery in 1877: none of the existing models can account simultaneously for their ubiquity, evolution, energetics and recently discovered periodicity. Here we report a synthesis of modelling and high-spatial-resolution observations in which numerical simulations driven by observed photospheric velocities directly reproduce the observed occurrence and properties of individual spicules. Photospheric velocities are dominated by convective granulation (which has been considered before for spicule formation) and by p-modes (which are solar global resonant acoustic oscillations visible in the photosphere as quasi-sinusoidal velocity and intensity pulsations). We show that the previously ignored p-modes are crucial: on inclined magnetic flux tubes, the p-modes leak sufficient energy from the global resonant cavity into the chromosphere to power shocks that drive upward flows and form spicules.

  13. On the generation of sound by turbulent convection. I - A numerical experiment. [in solar interior

    NASA Technical Reports Server (NTRS)

    Bogdan, Thomas J.; Cattaneo, Fausto; Malagoli, Andrea

    1993-01-01

    Motivated by the problem of the origin of the solar p-modes, we study the generation of acoustic waves by turbulent convection. Our approach uses the results of high-resolution 3D simulations as the experimental basis for our investigation. The numerical experiment describes the evolution of a horizontally periodic layer of vigorously convecting fluid. The sound is measured by a procedure, based on a suitable linearization of the equations of compressible convection that allows the amplitude of the acoustic field to be determined. Through this procedure we identify unambiguously some 400 acoustic modes. The total energy of the acoustic field is found to be a fraction of a percent of the kinetic energy of the convection. The amplitudes of the observed modes depend weakly on (horizontal) wavenumber but strongly on frequency. The line widths of the observed modes typically exceed the natural linewidths of the modes as inferred from linear theory. This broadening appears to be related to the (stochastic) interaction between the modes and the underlying turbulence which causes abrupt, episodic events during which the phase coherence of the modes is lost.

  14. Solar Radar Astronomy with LOFAR

    NASA Astrophysics Data System (ADS)

    Rodriguez, P.

    2003-04-01

    A new approach to the study of the Sun's corona and its dynamical processes is possible with radar investigations in the frequency range of about 10-50 MHz. The range of electron densities of the solar corona is such that radio waves at these frequencies can provide diagnostic radar echoes of large scale phenomena such as coronal mass ejections (CMEs). We expect that the frequency shift imposed on the echo signal by an earthward-moving CME will provide a direct measurement of the velocity, thereby providing a good estimate of the arrival time at Earth. It is known that CMEs are responsible for the largest geomagnetic storms at Earth, which are capable of causing power grid blackouts, satellite electronic upsets, and degradation of radio communications circuits. Thus, having accurate forecasts of potential CME-initiated geomagnetic storms is of practical space weather interest. New high power transmitting arrays are becoming available, along with proposed modifications to existing research facilities, that will allow the use of radio waves to study the solar corona by the radar echo technique. Of particular interest for such solar radar investigations is the bistatic configuration with the Low Frequency Array (LOFAR). The LOFAR facility will have an effective receiving area of about 1 square km at solar radar frequencies. Such large effective area will provide the receiving antenna gain needed for detailed investigations of solar coronal dynamics. Conservative estimates of the signal-to-noise ratio for solar radar echoes as a function of the integration time required to achieve a specified detection level (e.g., ~ 5 dB) indicate that time resolutions of 10s of seconds can be achieved. Thus, we are able to resolve variations in the solar radar cross section on time scales which will provide new information on the plasma dynamical processes associated with the solar corona, such as CMEs. It is the combination of high transmitted power and large effective receiving

  15. Variation of solar acoustic emission and its relation to phase of the solar cycle

    NASA Astrophysics Data System (ADS)

    Chen, Ruizhu; Zhao, Junwei

    2016-05-01

    Solar acoustic emission is closely related to solar convection and photospheric magnetic field. Variation of acoustic emission and its relation to the phase of solar cycles are important to understand dynamics of solar cycles and excitation of acoustic waves. In this work we use 6 years of SDO/HMI Dopplergram data to study acoustic emissions of the whole sun and of the quiet-sun regions, respectively, in multiple acoustic frequency bands. We show the variation of acoustic emission from May 2010 to April 2016, covering half of the solar cycle 24, and analyze its correlation with the solar activity level indexed by daily sunspot number and total magnetic flux. Results show that the correlation between the whole-Sun acoustic emission and the solar activity level is strongly negative for low frequencies between 2.5 and 4.5 mHz, but strongly positive for high frequencies between 4.5 and 6.0 mHz. For high frequencies, the acoustic emission excess in sunspot halos overwhelms the emission deficiency in sunspot umbrae and penumbrae. The correlation between the acoustic emission in quiet regions and the solar activity level is negative for 2.5-4.0 mHz and positive for 4.0-5.5 mHz. This shows that the solar background acoustic power, with active regions excluded, also varies during a solar cycle, implying the excitation frequencies or depths are highly related to the solar magnetic field.

  16. Solar Collectors

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Solar Energy's solar panels are collectors for a solar energy system which provides heating for a drive-in bank in Akron, OH. Collectors were designed and manufactured by Solar Energy Products, a firm established by three former NASA employees. Company President, Frank Rom, an example of a personnel-type technology transfer, was a Research Director at Lewis Research Center, which conducts extensive solar heating and cooling research, including development and testing of high-efficiency flat-plate collectors. Rom acquired solar energy expertise which helped the company develop two types of collectors, one for use in domestic/commercial heating systems and the other for drying grain.

  17. Solar coronal jets

    NASA Astrophysics Data System (ADS)

    Dobrzyck, D.

    The solar jets were first observed by SOHO instruments (EIT, LASCO, UVCS) during the previous solar minimum. They were small, fast ejections originating from flaring UV bright points within large polar coronal holes. The obtained data provided us with estimates of the jet plasma conditions, dynamics, evolution of the electron temperature and heating rate required to reproduce the observed ionization state. To follow the polar jets through the solar cycle a special SOHO Joint Observing Program (JOP 155) was designed. It involves a number of SOHO instruments (EIT, CDS, UVCS, LASCO) as well as TRACE. The coordinated observations have been carried out since April 2002. The data enabled to identify counterparts of the 1996-1998 solar minimum jets. Their frequency of several events per day appear comparable to the frequency from the previous solar minimum. The jets are believed to be triggered by field line reconnection between emerging magnetic dipole and pre-existing unipolar field. Existing models predict that the hot jet is formed together with another jet of a cool material. The particular goal of the coordinated SOHO and TRACE observations was to look for possible association of the hot and cool plasma ejections. Currently there is observational evidence that supports these models.

  18. Low Frequency Radio Experiment (LORE)

    NASA Astrophysics Data System (ADS)

    Manoharan, Periasamy K.; Joshi, Bhal Chandra; Naidu, Arun Kumar

    High temporal and frequency resolution observations of solar generated disturbances below 15 MHz in the near-Sun region and at Sun-Earth distances in conjunction with optical and high energy observations of Sun are essential to understand the structure and evolution of eruptions, such as, flares, coronal mass ejections (CMEs), and their associated solar wind disturbances at heights above the photosphere and their consequences in the interplanetary medium. This talk presents a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii below 30 MHz. The LORE, although not part of Aditya-L1 mission, can be complimentary to planned Aditya-L1 coronagraph and its other on-board payloads as well as synergistic to ground based observations, which are routinely carried out by Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and it is particularly suitable for providing data on the detailed time and frequency structure of fast drifting Type-III and slow drifting Type-II radio bursts with unprecedented time and frequency resolution as well as goniopolarimetry, made possible with better designed antennas and state-of-art electronics, employing FPGAs and an intelligent data management system. This would enable wide ranging studies such as studies of nonlinear plasma processes, CME in-situ radio emission, CME driven phenomena, interplanetary CME driven shocks, ICMEs driven by decelerating IP shocks and space weather effects of Solar Wind interaction regions. The talk will highlight the science objectives as well as the proposed technical design features.

  19. Solar-geophysical data number 577, September 1992. Part 2 (comprehensive reports), data for March 1992 and miscellaneous

    SciTech Connect

    Coffey, H.E.

    1992-09-01

    Contents: Detailed index for 1992; Data for March 1992 -- Solar flares, Solar radio bursts at fixed frequencies, Solar x-ray radiation from GOES satellite, Mass ejections from the sun, Active prominences and filaments, Solar irradiance; Miscellaneous data -- NIMBUS solar irradiance data Nov 78-Jun 92, NOAA SESC solar proton events Jan 76-Aug 92.

  20. Solar array flight experiment

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Emerging satellite designs require increasing amounts of electrical power to operate spacecraft instruments and to provide environments suitable for human habitation. In the past, electrical power was generated by covering rigid honeycomb panels with solar cells. This technology results in unacceptable weight and volume penalties when large amounts of power are required. To fill the need for large-area, lightweight solar arrays, a fabrication technique in which solar cells are attached to a copper printed circuit laminated to a plastic sheet was developed. The result is a flexible solar array with one-tenth the stowed volume and one-third the weight of comparably sized rigid arrays. An automated welding process developed to attack the cells to the printed circuit guarantees repeatable welds that are more tolerant of severe environments than conventional soldered connections. To demonstrate the flight readiness of this technology, the Solar Array Flight Experiment (SAFE) was developed and flown on the space shuttle Discovery in September 1984. The tests showed the modes and frequencies of the array to be very close to preflight predictions. Structural damping, however, was higher than anticipated. Electrical performance of the active solar panel was also tested. The flight performance and postflight data evaluation are described.

  1. Solar collectors

    SciTech Connect

    Cassidy, V.M.

    1981-11-01

    Practical applications of solar energy in commercial, industrial and institutional buildings are considered. Two main types of solar collectors are described: flat plate collectors and concentrating collectors. Efficiency of air and hydronic collectors among the flat plate types are compared. Also several concentrators are described, including their sun tracking mechanisms. Descriptions of some recent solar installations are presented and a list representing the cross section of solar collector manufacturers is furnished.

  2. Solar Equipment

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A medical refrigeration and a water pump both powered by solar cells that convert sunlight directly into electricity are among the line of solar powered equipment manufactured by IUS (Independent Utility Systems) for use in areas where conventional power is not available. IUS benefited from NASA technology incorporated in the solar panel design and from assistance provided by Kerr Industrial Applications Center.

  3. Solar reflector

    SciTech Connect

    Stone, D. C.

    1981-02-17

    A solar reflector having a flexible triangular reflective sheet or membrane for receiving and reflecting solar energy therefrom. The reflector is characterized by the triangular reflective sheet which is placed under tension thereby defining a smooth planar surface eliminating surface deflection which heretofore has reduced the efficiency of reflectors or heliostats used in combination for receiving and transmitting solar energy to an absorber tower.

  4. Buying Solar.

    ERIC Educational Resources Information Center

    Dawson, Joe

    Presented are guidelines for buying solar systems for the individual consumer. This is intended to help the consumer reduce many of the risks associated with the purchase of solar systems, particularly the risks of fraud and deception. Engineering terms associated with solar technology are presented and described to enable the consumer to discuss…

  5. Solar flair.

    PubMed Central

    Manuel, John S

    2003-01-01

    Design innovations and government-sponsored financial incentives are making solar energy increasingly attractive to homeowners and institutional customers such as school districts. In particular, the passive solar design concept of daylighting is gaining favor among educators due to evidence of improved performance by students working in daylit classrooms. Electricity-generating photovoltaic systems are also becoming more popular, especially in states such as California that have high electric rates and frequent power shortages. To help spread the word about solar power, the U.S. Department of Energy staged its first-ever Solar Decathlon in October 2002. This event featured solar-savvy homes designed by 14 college teams. PMID:12573926

  6. Solar Meter

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The instrument pictured is an inexpensive solar meter which is finding wide acceptance among architects, engineers and others engaged in construction of solar energy facilities. It detects the amount of solar energy available at a building site, information necessary to design the most efficient type of solar system for a particular location. Incorporating technology developed by NASA's Lewis Research Center, the device is based upon the solar cell, which provides power for spacecraft by converting the sun's energy to electricity. The meter is produced by Dodge Products, Inc., Houston, Texas, a company formed to bring the technology to the commercial marketplace.

  7. Solar flair.

    PubMed

    Manuel, John S

    2003-02-01

    Design innovations and government-sponsored financial incentives are making solar energy increasingly attractive to homeowners and institutional customers such as school districts. In particular, the passive solar design concept of daylighting is gaining favor among educators due to evidence of improved performance by students working in daylit classrooms. Electricity-generating photovoltaic systems are also becoming more popular, especially in states such as California that have high electric rates and frequent power shortages. To help spread the word about solar power, the U.S. Department of Energy staged its first-ever Solar Decathlon in October 2002. This event featured solar-savvy homes designed by 14 college teams.

  8. Solar Energy: Solar System Economics.

    ERIC Educational Resources Information Center

    Knapp, Henry H., III

    This module on solar system economics is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies.…

  9. Solar Sailing

    NASA Technical Reports Server (NTRS)

    Johnson, Les

    2009-01-01

    Solar sailing is a topic of growing technical and popular interest. Solar sail propulsion will make space exploration more affordable and offer access to destinations within (and beyond) the solar system that are currently beyond our technical reach. The lecture will describe solar sails, how they work, and what they will be used for in the exploration of space. It will include a discussion of current plans for solar sails and how advanced technology, such as nanotechnology, might enhance their performance. Much has been accomplished recently to make solar sail technology very close to becoming an engineering reality and it will soon be used by the world s space agencies in the exploration of the solar system and beyond. The first part of the lecture will summarize state-of-the-art space propulsion systems and technologies. Though these other technologies are the key to any deep space exploration by humans, robots, or both, solar-sail propulsion will make space exploration more affordable and offer access to distant and difficult destinations. The second part of the lecture will describe the fundamentals of space solar sail propulsion and will describe the near-, mid- and far-term missions that might use solar sails as a propulsion system. The third part of the lecture will describe solar sail technology and the construction of current and future sailcraft, including the work of both government and private space organizations.

  10. Properties of the Solar Acoustic Source Inferred from Nonadiabatic Oscillation Spectra

    NASA Astrophysics Data System (ADS)

    Wachter, R.; Kosovichev, A. G.

    2005-07-01

    Severino et al. suggested in 2001 that observed power and cross spectra of medium-degree p-modes in velocity and intensity can be described by splitting the solar background noise into correlated, coherent, and uncoherent components. We account for the nonadiabatic nature of solar oscillations by including the perturbations of the radiative energy flux in our model for the oscillations. Our calculations show the potential to explain the observations without the ad hoc phase differences between velocity and intensity oscillations introduced in the model of Severino et al. The phases and amplitudes of the correlated noise components are obtained by fitting our nonadiabatic model to the SOHO MDI power and cross spectra. These parameters provide information about the p-mode excitation process. We show that the type and location of the source can not be uniquely determined by the properties of the resonant p-modes in power and cross spectra of velocity and intensity oscillations. However, we obtain estimates for the phases and amplitudes of the correlated noise, which we interpret in terms of isolated rapid downdrafts in intergranular lanes. This idea is supported by three-dimensional simulations of the upper solar convection zone.

  11. Detection of Solar Oscillations (g-modes)

    NASA Astrophysics Data System (ADS)

    Homayouni, Y.; Ajabshirizadeh, A.

    2011-07-01

    Solar gravity modes are the best probes to study solar interior and specifically the dynamics of solar core. Here we present an analytical solution to solar gravity modes using relativistic space curvature inside 0.4 fractional radius with the assumption of mass accumulation inside the solar core. Considering the radial effect of gravitation, in order to calculate the spherical harmonics we have set the value of l to zero. Furthermore, a modified geometry for the interior regions of the Sun is presented. Consequently, a relation of g-mode frequency with fractional radius is calculated.

  12. PEP solar array definition study

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The conceptual design of a large, flexible, lightweight solar array is presented focusing on a solar array overview assessment, solar array blanket definition, structural-mechanical systems definition, and launch/reentry blanket protection features. The overview assessment includes a requirements and constraints review, the thermal environment assessment on the design selection, an evaluation of blanket integration sequence, a conceptual blanket/harness design, and a hot spot analysis considering the effects of shadowing and cell failures on overall array reliability. The solar array blanket definition includes the substrate design, hinge designs and blanket/harness flexibility assessment. The structural/mechanical systems definition includes an overall loads and deflection assessment, a frequency analysis of the deployed assembly, a components weights estimate, design of the blanket housing and tensioning mechanism. The launch/reentry blanket protection task includes assessment of solar cell/cover glass cushioning concepts during ascent and reentry flight condition.

  13. Observations of Solar Radio Transients

    NASA Astrophysics Data System (ADS)

    Paige, Giorla

    2011-05-01

    A low frequency radio telescope has been recently been constructed on the campus of the The College of New Jersey (TCNJ) and has begun conducting observations at 20MHz as part of NASA'a Radio Jove program. This instrument is capable of observations of solar radio emission including strong prompt radio emission associated with solar burst events. We will discuss solar observations conducted with this instrument as well as an effort to conduct coincident observations with the Eight-meter-wavelength Transient Array (ETA) and the Long Wavelength Array (LWA).

  14. Solar Simulator

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Oriel Corporation's simulators have a high pressure xenon lamp whose reflected light is processed by an optical system to produce a uniform solar beam. Because of many different types of applications, the simulators must be adjustable to replicate many different areas of the solar radiation spectrum. Simulators are laboratory tools for such purposes as testing and calibrating solar cells, or other solar energy systems, testing dyes, paints and pigments, pharmaceuticals and cosmetic preparations, plant and animal studies, food and agriculture studies and oceanographic research.

  15. Solar Physics

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    2000-01-01

    The areas of emphasis are: (1) develop theoretical models of the transient release of magnetic energy in the solar atmosphere, e.g., in solar flares, eruptive prominences, coronal mass ejections, etc.; (2) investigate the role of the Sun's magnetic field in the structuring of solar corona by the development of three-dimensional numerical models that describe the field configuration at various heights in the solar atmosphere by extrapolating the field at the photospheric level; (3) develop numerical models to investigate the physical parameters obtained by the ULYSSES mission; (4) develop numerical and theoretical models to investigate solar activity effects on the solar wind characteristics for the establishment of the solar-interplanetary transmission line; and (5) develop new instruments to measure solar magnetic fields and other features in the photosphere, chromosphere transition region and corona. We focused our investigation on the fundamental physical processes in solar atmosphere which directly effect our Planet Earth. The overall goal is to establish the physical process for the Sun-Earth connections.

  16. Solar luminosity oscillations from two stations and correlation with velocity measurements

    NASA Astrophysics Data System (ADS)

    Jimenez, A.; Palle, Pere L.; Roca Cortés, Teodoro; Andersen, N. B.; Domingo, V.; Jones, A. R.; Alvarez, M.; Ledezma, E.

    1988-12-01

    Since 1984 the measurements of a quadruple photometer sited at the Observatorio del Teide (Izana, Tenerife) made it possible to identify the p-mode luminosity spectrum with simultaneous velocity observations. Comparing this data, the adiabatic behavior of solar atmosphere and theoretical expectations from solar models were tested. In order to increase the signal-to-noise ratio and reduce the sidebands due to the night-time data gaps, a second identical photometer was set-up in December 1987, at the Observatorio de San Pedro Martir (Baja California Norte, Mexico). Results of the observations of these two stations are analyzed and compared with simultaneous velocity measurements.

  17. Average thermal characteristics of solar wind electrons

    NASA Technical Reports Server (NTRS)

    Montgomery, M. D.

    1972-01-01

    Average solar wind electron properties based on a 1 year Vela 4 data sample-from May 1967 to May 1968 are presented. Frequency distributions of electron-to-ion temperature ratio, electron thermal anisotropy, and thermal energy flux are presented. The resulting evidence concerning heat transport in the solar wind is discussed.

  18. Solar Eclipse

    Atmospheric Science Data Center

    2013-04-16

    ... a solar eclipse where an observer on Earth can watch the Moon's shadow obscure more than 90% the Sun's disk, the Multiangle Imaging ... total solar eclipse of November 23, 2003. The path of the Moon's umbral shadow began in the Indian Ocean in the far Southern Hemisphere, ...

  19. Solar Eclipse

    Atmospheric Science Data Center

    2013-04-19

    ...   View Larger Image On June 10, 2002 the Moon obscured the central portion of the solar disk in a phenomenon known as an ... in which 99.6 percent of the solar disk was shadowed by the Moon, was situated in the central Pacific Ocean. Since there are no populated ...

  20. Solar Sprint

    ERIC Educational Resources Information Center

    Tabor, Richard; Anderson, Stephen

    2007-01-01

    In the "Solar Sprint" activity, students design, test, and race a solar-powered car built with Legos. The use of ratios is incorporated to simulate the actual work of scientists and engineers. This method encourages fourth-grade students to think about multiple variables and stimulates their curiosity when an activity doesn't come out as…

  1. Solar Technologies

    ERIC Educational Resources Information Center

    von Hippel, Frank; Williams, Robert H.

    1975-01-01

    As fossil fuels decrease in availability and environmental concerns increase, soalr energy is becoming a potential major energy source. Already solar energy is used for space heating in homes. Proposals for solar-electric generating systems include land-based or ocean-based collectors and harnessing wind and wave power. Photosynthesis can also…

  2. Probing the Fundamental Physics of the Solar Corona with Lunar Solar Occultation Observations

    NASA Astrophysics Data System (ADS)

    Habbal, S. Rifai; Morgan, H.; Druckmüller, M.; Ding, A.; Cooper, J. F.; Daw, A.; Sittler, E. C.

    2013-07-01

    Imaging and spectroscopy of the solar corona, coupled with polarimetry, are the only tools available at present to capture signatures of physical processes responsible for coronal heating and solar wind acceleration within the first few solar radii above the solar limb. With the recent advent of improved detector technology and image processing techniques, broad-band white light and narrow-band multi-wavelength observations of coronal forbidden lines, made during total solar eclipses, have started to yield new views about the thermodynamic and magnetic properties of coronal structures. This paper outlines these unique capabilities, which until present, have been feasible primarily with observations during natural total solar eclipses. This work also draws attention to the exciting possibility of greatly increasing the frequency and duration of solar eclipse observations with Moon orbiting observatories utilizing lunar limb occultation of the solar disk for coronal measurements.

  3. Solar-Geophysical Data Number 542, October 1989. Part 2 (comprehensive reports). Data for April 1989 and miscellaneous

    SciTech Connect

    Coffey, H.E.

    1989-10-01

    Contents: detailed index for 1989; data for April 1989 -- solar flares, solar radio bursts at fixed frequencies, interplanetary solar particles and plasma, solar x-ray radiation from GOES satellite, mass ejections from the sun, active prominences and filaments; miscellaneous data -- Meudon Carte synoptique carrington rotations 1811-1812, solar ultraviolet radiation Nimbus 7 November 1978-October 1984.

  4. Solar ponds

    SciTech Connect

    Jayadev, T.S.; Edesess, M.

    1980-04-01

    This report first describes the different types of solar ponds including the nonconvecting salt gradient pond and various saltless pond designs. It then discusses the availability and cost of salts for salt gradient ponds, and compares the economics of salty and saltless ponds as a function of salt cost. A simple computational model is developed to approximate solar pond performance. This model is later used to size solar ponds for district heating and industrial process heat applications. For district heating, ponds are sized to provide space conditioning for a group of homes, in different regions of the United States. Size requirements is on the order of one acre for a group of 25 to 50 homes. An economic analysis is performed of solar ponds used in two industrial process heat applications. The analysis finds that solar ponds are competitive when conventional heat sources are priced at $5 per million Btu and expected to rise in price at a rate of 10% per year. The application of solar ponds to the generation of electricity is also discussed. Total solar pond potential for displacing conventional energy sources is estimated in the range of from one to six quadrillion Btu per year in the near and intermediate future.

  5. Solar sail

    SciTech Connect

    Drexler, K.E.

    1986-09-30

    This patent describes a solar sail propulsion system comprising: solar sail means for intercepting light pressure to produce thrust, the solar sail means being a thin metal film; tension truss means having two ends attached at one end to the solar sail means for transferring the thrust from the solar sail and for preventing gross deformation of the solar sail under light pressure, the solar sail means being a plurality of separate generally two-dimensional pieces joined by springs to the tension truss means; a payload attached to the other end of the tension truss means, the tension truss means comprising a plurality of attachment means for attaching shroud lines to the top of the tension truss means and a plurality of the shroud lines attached to the attachment means at one of their ends and the payload at the other; a plurality of reel means attached to the shroud lines for controllably varying the length of the lines; and a plurality of reflective panel means attached to the sail means for controlling the orientation of the system.

  6. Solar-Geophysical Data Number 564, August 1991. Part 2 (Comprehensive reports). Data for February 1991 and miscellaneous

    SciTech Connect

    Coffey, H.E.

    1991-08-01

    The contents include: Detailed index for 1990-1991; Data for February 1991--Solar flares, Solar radio bursts at fixed frequencies, Interplanetary solar particles and plasma, Solar X-ray radiation from GOES satellite, Mass ejections from the sun, Active prominences and filaments; Miscellaneous data--Interplanetary solar particles and plasma--IMP 8 solar wind October 1990-January 1991, Total solar irradiance--NIMBUS November 1978-April 1991.

  7. Solar extreme events

    NASA Astrophysics Data System (ADS)

    Hudson, Hugh S.

    2015-08-01

    Solar flares and CMEs have a broad range of magnitudes. This review discusses the possibility of “extreme events,” defined as those with magnitudes greater than have been seen in the existing historical record. For most quantitative measures, this direct information does not extend more than a century and a half into the recent past. The magnitude distributions (occurrence frequencies) of solar events (flares/CMEs) typically decrease with the parameter measured or inferred (peak flux, mass, energy etc. Flare radiation fluxes tend to follow a power law slightly flatter than S-2, where S represents a peak flux; solar particle events (SPEs) follow a still flatter power law up to a limiting magnitude, and then appear to roll over to a steeper distribution, which may take an exponential form or follow a broken power law. This inference comes from the terrestrial 14C record and from the depth dependence of various radioisotope proxies in the lunar regolith and in meteorites. Recently major new observational results have impacted our use of the relatively limited historical record in new ways: the detection of actual events in the 14C tree-ring records, and the systematic observations of flares and “superflares” by the Kepler spacecraft. I discuss how these new findings may affect our understanding of the distribution function expected for extreme solar events.

  8. Solar pruritus.

    PubMed

    Bech-Thomsen, N; Thomsen, K

    1995-11-01

    A case of solar pruritus is reported. Severe pruritus of the back, shoulders and upper lateral aspects of the arms, without any eruption, developed in a 28-year-old outdoor worker during 4 to 6 weeks of intensive solar exposure. The pruritus was intense and described as a burning sensation deep in the skin. Only a few excoriations and slight xerosis were found. Solar pruritus or brachioradial pruritus is a condition primarily seen in Caucasian people living in the tropics or subtropics. Previously the disease has only been reported once outside these areas.

  9. Solar Two

    SciTech Connect

    Not Available

    1998-04-01

    Solar Two is a concentrating solar power plant that can supply electric power on demand to the local utility, Southern California Edison Company. It can do so because it operates not only during sunny parts of the day, but it can store enough thermal energy from the sun to operate during cloudy periods and after dark, for up to three hours, at its rated output of 10 megawatts (MW). For the first time ever, a utility scale solar power plant can supply electricity when the utility needs it most, to satisfy the energy requirements of its customers.

  10. Solar-geophysical data number 496, December 1985. Part 2: (Comprehensive reports). Data for June 1985, January-May 1985 and miscellanea

    NASA Technical Reports Server (NTRS)

    Coffey, H. E. (Editor)

    1985-01-01

    Contents include the detailed index for 1985; data for June 1985 (solar flares, solar radio bursts at fixed frequencies, solar X-ray radiation from GOES satellite graphs, mass ejections from the sun, and active prominences and filaments); data for January to May 1985 (solar flares January 1985, solar flares February 1985, solar flares March 1985, solar flares April 1985, solar flares May 1985, and number of flares August 1966 to June 1985); and the international geophysical calendar 1986.

  11. Solar fuels

    NASA Astrophysics Data System (ADS)

    Viitanen, M.

    1990-12-01

    The aim of this paper is to give a review concerning the storage of solar energy by converting it to chemical energy. This is based on several articles published during the last fifteen years. The methods to convert solar energy to chemical energy, e.g., to produce hydrogen, can be divided into three different methods. The most common one is probably the usage of solar cells; thus the solar energy is first converted into electrical energy and further the water is split electrochemically to produce hydrogen. It could be also done in a photoelectrochemical cell, or simply photochemically. A photobiological system can also be considered as a photochemical system, although it is discussed separately from the photochemical systems. These three last mentioned methods will be discussed in this paper.

  12. Solar Nexus.

    ERIC Educational Resources Information Center

    Murphy, Jim

    1980-01-01

    The design team for the Solar Energy Research Institute (SERI) has pushed the state of the energy art to its current limits for the initial phase, with provisions for foreseeable and even speculative future applications. (Author/MLF)

  13. Solar chulha

    NASA Astrophysics Data System (ADS)

    Jadhao, P. H.; Patrikar, S. R.

    2016-05-01

    The main goal of the proposed system is to transfer energy from sun to the cooking load that is located in the kitchen. The energy is first collected by the solar collector lens system and two curve bars of same radius of curvature are mounted parallel and adjacent to each other at different height the solar collector is clamed on this two bars such that solar collector is exactly perpendicular to sunlight. The topology includes an additional feature which is window in the wall through which the beam is collimated is directed in the of kitchen. The solar energy that is collected is directed by the mirror system into the kitchen, where it is redirected to cooking platform located in the kitchen. The special feature in this system full Indian meal can be made since cooking platform is indoors.

  14. Metasurface Broadband Solar Absorber

    PubMed Central

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-01-01

    We demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure. PMID:26828999

  15. Metasurface Broadband Solar Absorber

    DOE PAGES

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; ...

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributionsmore » to elucidate how the absorption occurs within the metasurface structure.« less

  16. Metasurface Broadband Solar Absorber

    SciTech Connect

    Azad, Abul K.; Kort-Kamp, Wilton J. M.; Sykora, Milan; Weisse-Bernstein, Nina R.; Luk, Ting S.; Taylor, Antoinette J.; Dalvit, Diego A. R.; Chen, Hou-Tong

    2016-02-01

    Here, we demonstrate a broadband, polarization independent, wide-angle absorber based on a metallic metasurface architecture, which accomplishes greater than 90% absorptance in the visible and near-infrared range of the solar spectrum, and exhibits low absorptivity (emissivity) at mid- and far-infrared wavelengths. The complex unit cell of the metasurface solar absorber consists of eight pairs of gold nano-resonators that are separated from a gold ground plane by a thin silicon dioxide spacer. Moreover, our experimental measurements reveal high-performance absorption over a wide range of incidence angles for both s- and p-polarizations. We also investigate numerically the frequency-dependent field and current distributions to elucidate how the absorption occurs within the metasurface structure.

  17. Theoretical studies of the physics of the solar atmosphere

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1992-01-01

    Significant advances in our theoretical basis for understanding several physical processes related to dynamical phenomena on the sun were achieved. We have advanced a new model for spicules and fibrils. We have provided a simple physical view of resonance absorption of MHD surface waves; this allowed an approximate mathematical procedure for obtaining a wealth of new analytical results which we applied to coronal heating and p-mode absorption at magnetic regions. We provided the first comprehensive models for the heating and acceleration of the transition region, corona, and solar wind. We provided a new view of viscosity under coronal conditions. We provided new insights into Alfven wave propagation in the solar atmosphere. And recently we have begun work in a new direction: parametric instabilities of Alfven waves.

  18. Wave Modeling of the Solar Wind.

    PubMed

    Ofman, Leon

    The acceleration and heating of the solar wind have been studied for decades using satellite observations and models. However, the exact mechanism that leads to solar wind heating and acceleration is poorly understood. In order to improve the understanding of the physical mechanisms that are involved in these processes a combination of modeling and observational analysis is required. Recent models constrained by satellite observations show that wave heating in the low-frequency (MHD), and high-frequency (ion-cyclotron) range may provide the necessary momentum and heat input to coronal plasma and produce the solar wind. This review is focused on the results of several recent solar modeling studies that include waves explicitly in the MHD and the kinetic regime. The current status of the understanding of the solar wind acceleration and heating by waves is reviewed.

  19. Correlation between solar acoustic emission and phase of the solar cycle

    NASA Astrophysics Data System (ADS)

    Chen, R.; Zhao, J.

    2015-12-01

    The solar acoustic emission is closely related to solar convection and magnetic field. Understanding the relation between the acoustic emission and the phase of a solar cycle is important to understand the dynamics of solar cycles and excitation of acoustic waves. In this work we use 4 years of SDO/HMI data from 05/2010 to 04/2014, covering the growing phase of the solar cycle 24, to study the acoustic emissions of the whole sun and of only the quiet sun regions respectively, at multiple frequency bands. We also analyze the correlations between the acoustic emissions and solar activity level indexed by daily sunspot number and magnetic flux. The results show that the correlation between the whole-sun acoustic emission and solar activity level is negative for low frequencies at 2.5-4.5 mHz, with a peak value around -0.9, and is positive for high frequencies at 4.5-6.0 mHz, with a peak value around 0.9. For high frequencies, the acoustic emission excess in sunspot halos overwhelms the emission deficiency in sunspot umbrae and penumbrae. The correlation between the quiet-sun acoustic emission and solar activity level is negative for 2.5-4.0 mHz and positive for 4.0-5.5 mHz, with peak values over ±0.8. This shows that the solar background acoustic power, with active regions excluded, is indeed varying during a solar cycle, implying the excitation frequencies or depths are highly related to the solar magnetic field.

  20. Solar Pump

    NASA Technical Reports Server (NTRS)

    Pique, Charles

    1987-01-01

    Proposed pump moves liquid by action of bubbles formed by heat of sun. Tube of liquid having boiling point of 100 to 200 degrees F placed at focal axis of cylindrical reflector. Concentrated sunlight boils liquid at focus, and bubbles of vapor rise in tube, carrying liquid along with them. Pressure difference in hot tube sufficient to produce flow in large loop. Used with conventional flat solar heating panel in completely solar-powered heat-storage system.

  1. Solar Cells

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The Heat Exchanger Method (HEM) produces high efficiency crystal ingots in an automated well-insulated furnace offering low equipment, labor and energy costs. The "grown" silicon crystals are used to make solar cells, or photovoltaic cells which convert sunlight directly into electricity. The HEM method is used by Crystal Systems, Inc. and was developed under a NASA/Jet Propulsion Laboratory contract. The square wafers which are the result of the process are sold to companies manufacturing solar panels.

  2. Solar Schematic

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The home shown at right is specially designed to accommodate solar heating units; it has roof planes in four directions, allowing placement of solar collectors for best exposure to the sun. Plans (bottom) and complete working blueprints for the solar-heated house are being marketed by Home Building Plan Service, Portland, Oregon. The company also offers an inexpensive schematic (center) showing how a homeowner only moderately skilled in the use of tools can build his own solar energy system, applicable to new or existing structures. The schematic is based upon the design of a low-cost solar home heating system built and tested by NASA's Langley Research Center; used to supplement a warm-air heating system, it can save the homeowner about 40 percent of his annual heating bill for a modest investment in materials and components. Home Building Plan Service saved considerable research time by obtaining a NASA technical report which details the Langley work. The resulting schematic includes construction plans and simplified explanations of solar heat collection, collectors and other components, passive heat factors, domestic hot water supply and how to work with local heating engineers.

  3. NO2 photolysis frequencies in street canyons

    NASA Astrophysics Data System (ADS)

    Koepke, P.; Garhammer, M.; Hess, M.; Roeth, E.-P.

    2010-08-01

    Photolysis frequencies for NO2 are modeled for the conditions in urban streets, which are taken into account as canyons with variable height and width. The effect of a street canyon is presented with absolute values and as a ratio RJ of the photolysis frequency within the street compared to that with free horizon. This allows further use of the existing photolysis parameterizations. Values are presented for variable solar elevation and azimuth angles, varying atmospheric conditions and different street properties. The NO2 photolysis frequency in a street depends strongly on the relative width of the street and its orientation towards the sun. Averaged over atmospheric conditions and street orientation, the NO2 photolysis frequency is reduced in comparison with the values for free horizon: to less than 20% for narrow skyscraper streets, to about 40% for typical urban streets, and only to about 80% for garden streets. A parameterization with the global solar irradiance is given for the averaged RJ values.

  4. Periodic solar wind density structures

    NASA Astrophysics Data System (ADS)

    Viall, Nicholeen Mary

    2010-01-01

    This dissertation addresses a specific aspect of the Sun-Earth connection: we show that coronal activity creates periodic density structures in the solar wind which convect radially outward and interact with Earth's magnetosphere. First, we analyze 11 years (1995-2005) of in situ solar wind density observations from the Wind spacecraft and find that periodic density structures occur at particular sets of radial length-scales more often than others. This indicates that these density fluctuations, which have radial length-scales of hundreds of megameters, cannot be attributed entirely to turbulence. Next, we analyze their effect on Earth's magnetosphere. Though these structures are not waves in the solar wind rest frame, they appear at discrete frequencies in Earth's reference frame. They compress the magnetosphere as they convect past, driving global magnetospheric oscillations at the same discrete frequencies as the periodic density structures. Last, we investigate source regions and mechanisms of the periodic solar wind density structures. We analyze the alpha particle to proton abundance ratio during events of periodic density structures. In many events, the proton and alpha density fluctuations are anti- correlated, which strongly argues for either temporally or spatially varying coronal source plasma. We examine white light images of the solar wind taken with SECCHI HI1 on the STEREO spacecraft and find periodic density structures as near to the Sun as 15 solar radii. The smallest resolvable periodic structures that we identify are of comparable length to those found at 1 AU, providing further evidence that at least some periodic density structures are generated in the solar corona as the solar wind is formed. Guided by the properties observed during previous studies and the characteristics established through the work presented here, we examine possible candidate mechanisms in the solar corona that can form periodic density structures. We conclude that

  5. Asymptotic theory of intermediate- and high-degree solar acoustic oscillations

    NASA Technical Reports Server (NTRS)

    Brodsky, M.; Vorontsov, S. V.

    1993-01-01

    A second-order asymptotic approximation is developed for adiabatic nonradial p-modes of a spherically symmetric star. The exact solutions of adiabatic oscillations are assumed in the outermost layers, where the asymptotic description becomes invalid, which results in a eigenfrequency equation with model-dependent surface phase shift. For lower degree modes, the phase shift is a function of frequency alone; for high-degree modes, its dependence on the degree is explicitly taken into account.

  6. Microwave Frequency Multiplier

    NASA Astrophysics Data System (ADS)

    Velazco, J. E.

    2017-02-01

    High-power microwave radiation is used in the Deep Space Network (DSN) and Goldstone Solar System Radar (GSSR) for uplink communications with spacecraft and for monitoring asteroids and space debris, respectively. Intense X-band (7.1 to 8.6 GHz) microwave signals are produced for these applications via klystron and traveling-wave microwave vacuum tubes. In order to achieve higher data rate communications with spacecraft, the DSN is planning to gradually furnish several of its deep space stations with uplink systems that employ Ka-band (34-GHz) radiation. Also, the next generation of planetary radar, such as Ka-Band Objects Observation and Monitoring (KaBOOM), is considering frequencies in the Ka-band range (34 to 36 GHz) in order to achieve higher target resolution. Current commercial Ka-band sources are limited to power levels that range from hundreds of watts up to a kilowatt and, at the high-power end, tend to suffer from poor reliability. In either case, there is a clear need for stable Ka-band sources that can produce kilowatts of power with high reliability. In this article, we present a new concept for high-power, high-frequency generation (including Ka-band) that we refer to as the microwave frequency multiplier (MFM). The MFM is a two-cavity vacuum tube concept where low-frequency (2 to 8 GHz) power is fed into the input cavity to modulate and accelerate an electron beam. In the second cavity, the modulated electron beam excites and amplifies high-power microwaves at a frequency that is a multiple integer of the input cavity's frequency. Frequency multiplication factors in the 4 to 10 range are being considered for the current application, although higher multiplication factors are feasible. This novel beam-wave interaction allows the MFM to produce high-power, high-frequency radiation with high efficiency. A key feature of the MFM is that it uses significantly larger cavities than its klystron counterparts, thus greatly reducing power density and arcing

  7. Solar radio emission

    NASA Technical Reports Server (NTRS)

    Goldman, M. V.; Smith, D. F.

    1981-01-01

    Active areas of both observational and theoretical research in which rapid progress is being made are discussed. These include: (1) the dynamic spectrum or frequency versus time plot; (2) physical mechanisms in the development of various types of bursts; (3) microwave type 1, 2, 3, and moving type 4 bursts; (4) bursts caused by trapped electrons; (5) physics of type 3bursts; (6) the physics of type 2 bursts and their related shocks; (7) the physics of both stationary and moving traps and associated type 1 and moving type 4 bursts; and (8) the status of the field of solar radio emission.

  8. SURFACE WAVES IN SOLAR GRANULATION OBSERVED WITH SUNRISE

    SciTech Connect

    Roth, M.; Franz, M.; Bello Gonzalez, N.; Berkefeld, T.; Schmidt, W.; Martinez Pillet, V.; Bonet, J. A.; Del Toro Iniesta, J. C.; Domingo, V.; Knoelker, M.

    2010-11-10

    Solar oscillations are expected to be excited by turbulent flows in the intergranular lanes near the solar surface. Time series recorded by the IMaX instrument on board the SUNRISE observatory reveal solar oscillations at high spatial resolution, which allow the study of the properties of oscillations with short wavelengths. We analyze two time series with synchronous recordings of Doppler velocity and continuum intensity images with durations of 32 minutes and 23 minutes, respectively, recorded close to the disk center of the Sun to study the propagation and excitation of solar acoustic oscillations. In the Doppler velocity data, both the standing acoustic waves and the short-lived, high-degree running waves are visible. The standing waves are visible as temporary enhancements of the amplitudes of the large-scale velocity field due to the stochastic superposition of the acoustic waves. We focus on the high-degree small-scale waves by suitable filtering in the Fourier domain. Investigating the propagation and excitation of f- and p {sub 1}-modes with wavenumbers k>1.4 Mm{sup -1}, we also find that exploding granules contribute to the excitation of solar p-modes in addition to the contribution of intergranular lanes.

  9. Solar ponds

    NASA Astrophysics Data System (ADS)

    Tabor, H.

    1981-01-01

    The history and current status of salt-gradient non-convecting solar ponds are presented. These ponds are large-area collectors, capable of providing low-cost thermal, mechanical, or electrical energy using low-temperature turbo-generators. The basic theory of salt-gradient solar ponds is sketched; the effects of wind, leakage, and fouling and their constraints on location selection for solar ponds are discussed. The methods of building and filling the ponds, as well as extracting heat from them are explained in detail. Practical operating temperatures of 90 C can be obtained with collection efficiencies between 15% and 25%, demonstrating the practical use of the ponds for heating and cooling purposes, power production, and desalination. A condensed account of solar pond experience in several countries is given. This includes the 150 kW solar pond power station (SPPS) operating in Israel since December, 1979 and a 5000 kW unit currently under development. A study of the economics involved in using the ponds is presented: despite a low conversion efficiency, the SPPS is shown to have applications in many countries.

  10. Solar ADEPT: Efficient Solar Energy Systems

    SciTech Connect

    2011-01-01

    Solar ADEPT Project: The 7 projects that make up ARPA-E's Solar ADEPT program, short for 'Solar Agile Delivery of Electrical Power Technology,' aim to improve the performance of photovoltaic (PV) solar energy systems, which convert the sun's rays into electricity. Solar ADEPT projects are integrating advanced electrical components into PV systems to make the process of converting solar energy to electricity more efficient.

  11. Solar Minimum

    NASA Astrophysics Data System (ADS)

    Lopresto, James C.; Mathews, John; Manross, Kevin

    1995-12-01

    Calcium K plage, H alpha plage and sunspot area have been monitored daily on the INTERNET since November of 1992. The plage and sunspot area have been measured by image processing. The purpose of the project is to investigate the degree of correlation between plage area and solar irradiance. The plage variation shows the expected variation produced by solar rotation and the longer secular changes produced by the solar cycle. The H alpha and sunspot plage area reached a minimum in about late 1994 or early 1995. This is in agreement with the K2 spectral index obtained daily from Sacramento Peak Observatory. The Calcium K plage area minimum seems delayed with respect to the others mentioned above. The minimum of the K line plage area is projected to come within the last few months of 1995.

  12. Solar Neutrinos

    DOE R&D Accomplishments Database

    Davis, R. Jr.; Harmer, D. S.

    1964-12-01

    The prospect of studying the solar energy generation process directly by observing the solar neutrino radiation has been discussed for many years. The main difficulty with this approach is that the sun emits predominantly low energy neutrinos, and detectors for observing low fluxes of low energy neutrinos have not been developed. However, experimental techniques have been developed for observing neutrinos, and one can foresee that in the near future these techniques will be improved sufficiently in sensitivity to observe solar neutrinos. At the present several experiments are being designed and hopefully will be operating in the next year or so. We will discuss an experiment based upon a neutrino capture reaction that is the inverse of the electron-capture radioactive decay of argon-37. The method depends upon exposing a large volume of a chlorine compound, removing the radioactive argon-37 and observing the characteristic decay in a small low-level counter.

  13. Solar flare particle radiation

    NASA Technical Reports Server (NTRS)

    Lanzerotti, L. J.

    1972-01-01

    The characteristics of the solar particles accelerated by solar flares and subsequently observed near the orbit of the earth are studied. Considered are solar particle intensity-time profiles, the composition and spectra of solar flare events, and the propagation of solar particles in interplanetary space. The effects of solar particles at the earth, riometer observations of polar cap cosmic noise absorption events, and the production of solar cell damage at synchronous altitudes by solar protons are also discussed.

  14. Long-Period Solar Variability

    SciTech Connect

    GAUTHIER,JOHN H.

    2000-07-20

    Terrestrial climate records and historical observations of the Sun suggest that the Sun undergoes aperiodic oscillations in radiative output and size over time periods of centuries and millenia. Such behavior can be explained by the solar convective zone acting as a nonlinear oscillator, forced at the sunspot-cycle frequency by variations in heliomagnetic field strength. A forced variant of the Lorenz equations can generate a time series with the same characteristics as the solar and climate records. The timescales and magnitudes of oscillations that could be caused by this mechanism are consistent with what is known about the Sun and terrestrial climate.

  15. Solar panel

    SciTech Connect

    Bayles, B.R.

    1981-09-29

    A solar panel includes a base within which are mounted transversely extending conduits. A heat collector plate in the base is in heat conductive relationship with the conduits for the heating of a fluid medium. The base additionally supports a transparent cover outwardly spaced from the heat collector plate to provide a protective insulative air space over the plate. A manifold communicates one series of panels with those of an adjacent series. A modified base dispenses with a collector plate and is formed so as to define integral lengthwise extending passageways for the solar heated medium. Inserted nipples interconnect the passageways of adjacent panels.

  16. Solar trap

    SciTech Connect

    Lew, H.S.

    1988-02-09

    A solar trap for collecting solar energy at a concentrated level is described comprising: (a) a compound light funnel including a pair of light reflecting substantially planar members arranged into a trough having a substantially V-shaped cross section; (b) a two dimensional Fresnel lens cover covering the opening of the compound light funnel, the opening being the open diverging end of the substantially V-shaped cross section of the compound light funnel; (c) at least one conduit for carrying a heat transfer fluid disposed substantially adjacent and substantially parallel to the apex line of the compound light funnel.

  17. Solar Energy and You.

    ERIC Educational Resources Information Center

    Conservation and Renewable Energy Inquiry and Referral Service (DOE), Silver Spring, MD.

    This booklet provides an introduction to solar energy by discussing: (1) how a home is heated; (2) how solar energy can help in the heating process; (3) the characteristics of passive solar houses; (4) the characteristics of active solar houses; (5) how solar heat is stored; and (6) other uses of solar energy. Also provided are 10 questions to…

  18. Solar maximum: Solar array degradation

    NASA Technical Reports Server (NTRS)

    Miller, T.

    1985-01-01

    The 5-year in-orbit power degradation of the silicon solar array aboard the Solar Maximum Satellite was evaluated. This was the first spacecraft to use Teflon R FEP as a coverglass adhesive, thus avoiding the necessity of an ultraviolet filter. The peak power tracking mode of the power regulator unit was employed to ensure consistent maximum power comparisons. Telemetry was normalized to account for the effects of illumination intensity, charged particle irradiation dosage, and solar array temperature. Reference conditions of 1.0 solar constant at air mass zero and 301 K (28 C) were used as a basis for normalization. Beginning-of-life array power was 2230 watts. Currently, the array output is 1830 watts. This corresponds to a 16 percent loss in array performance over 5 years. Comparison of Solar Maximum Telemetry and predicted power levels indicate that array output is 2 percent less than predictions based on an annual 1.0 MeV equivalent election fluence of 2.34 x ten to the 13th power square centimeters space environment.

  19. What have we learned about the solar interior from solar oscillations?

    SciTech Connect

    Guzik, J.A.

    1995-12-31

    After a brief review of the discovery and properties of solar oscillations, I summarize the significant advances in our knowledge of the Sun`s interior structure achieved by using solar oscillation frequency data. I discuss the surprising solar interior rotation profile; the precise determination of the convection zone depth; the convection zone helium abundance; evidence for diffusive settling of helium during the Sun`s 4.5 billion year lifetime; and the Sun`s central structure and implications for the solar neutrino problem.

  20. Obliquity Modulation of the Incoming Solar Radiation

    NASA Technical Reports Server (NTRS)

    Liu, Han-Shou; Smith, David E. (Technical Monitor)

    2001-01-01

    Based on a basic principle of orbital resonance, we have identified a huge deficit of solar radiation induced by the combined amplitude and frequency modulation of the Earth's obliquity as possibly the causal mechanism for ice age glaciation. Including this modulation effect on solar radiation, we have performed model simulations of climate change for the past 2 million years. Simulation results show that: (1) For the past 1 million years, temperature fluctuation cycles were dominated by a 100-Kyr period due to amplitude-frequency resonance effect of the obliquity; (2) From 2 to 1 million years ago, the amplitude-frequency interactions. of the obliquity were so weak that they were not able to stimulate a resonance effect on solar radiation; (3) Amplitude and frequency modulation analysis on solar radiation provides a series of resonance in the incoming solar radiation which may shift the glaciation cycles from 41-Kyr to 100-Kyr about 0.9 million years ago. These results are in good agreement with the marine and continental paleoclimate records. Thus, the proposed climate response to the combined amplitude and frequency modulation of the Earth's obliquity may be the key to understanding the glaciation puzzles in paleoclimatology.

  1. SOLAR NANTENNA ELECTROMAGNETIC COLLECTORS

    SciTech Connect

    Steven D. Novack; Dale K. Kotter; Dennis Slafer; Patrick Pinhero

    2008-08-01

    This research explores a new efficient approach for producing electricity from the abundant energy of the sun. A nanoantenna electromagnetic collector (NEC) has been designed, prototyped, and tested. Proof of concept has been validated. The device targets mid-infrared wavelengths where conventional photovoltaic (PV) solar cells do not respond but is abundant in solar energy. The initial concept of designing NEC antennas was based on scaling of radio frequency antenna theory. This approach has proven unsuccessful by many due to not fully understanding and accounting for the optical behavior of materials in the THz region. Also until recent years the nanofabrication methods were not available to fabricate the optical antenna elements. We have addressed and overcome both technology barriers. Several factors were critical in successful implementation of NEC including: 1) frequency-dependent modeling of antenna elements, 2) selection of materials with proper THz properties and 3) novel manufacturing methods that enable economical large-scale manufacturing. The work represents an important step toward the ultimate realization of a low-cost device that will collect as well as convert this radiation into electricity, which will lead to a wide spectrum, high conversion efficiency, and low cost solution to complement conventional PVs.

  2. Solar Power

    ERIC Educational Resources Information Center

    Ford, Norman C.; Kane, Joseph W.

    1971-01-01

    Proposes a method of collecting solar energy by using available plastics for Fresnel lenses to focus heat onto a converter where thermal dissociation of water would produce hydrogen. The hydrogen would be used as an efficient non-polluting fuel. Cost estimates are included. (AL)

  3. Solar Directory.

    ERIC Educational Resources Information Center

    Pesko, Carolyn, Ed.

    This directory is designed to help the researcher and developer, the manufacturer and distributor, and the general public communicate together on a mutually beneficial basis. Its content covers the wide scope of solar energy activity in the United States primarily, but also in other countries, at the academic, governmental, and industrial levels.…

  4. Solar cooker

    SciTech Connect

    Long, J. B.; Ware, R. R.

    1985-12-31

    A solar cooking device made of a flat array of concentric mirrors tilted to focus at a small area, the array being movable mounted on a stand to be movable around a ball joint and with a carrier for a cooking vessel held by a double crank to be at the focal area of the mirrors.

  5. Testing solar models with global solar oscillations in the 5-minute band

    NASA Technical Reports Server (NTRS)

    Ulrich, R. K.; Rhodes, E. J., Jr.

    1983-01-01

    Frequencies of solar oscillation for normal modes described by spherical harmonics with l-values between 0 and 4 are computed. The method of computation is discussed and some of the theoretical uncertainties are examined. It is shown that the standard solar model has eigenfrequencies which do not agree with the frequencies observed for the low l-modes to within the estimated accuracy of either the observed or theoretical frequencies. Four non-standard models are considered: (1) the interior Z abundance is lower than the surface abundance; (2) the interior Z abundance is higher than the surface abundance; (3) the interior Z abundance is altered by mixing; and (4) a large primordial magnetic field remains in the solar core. The effect of all these models on the solar neutrino flux is considered, with the result that the high-Z model is rejected. The conclusions of Bahcall and Ulrich (1971) that a primordial magnetic field increases the neutrino flux are disputed.

  6. Solar electric systems

    SciTech Connect

    Warfield, G.

    1984-01-01

    Electricity from solar sources is the subject. The state-of-the-art of photovoltaics, wind energy and solar thermal electric systems is presented and also a broad range of solar energy activities throughout the Arab world is covered. Contents, abridged: Solar radiation fundamentals. Basic theory solar cells. Solar thermal power plants. Solar energy activities at the scientific research council in Iraq. Solar energy program at Kuwait Institute for Scientific Research. Prospects of solar energy for Egypt. Non-conventional energy in Syria. Wind and solar energies in Sudan. Index.

  7. NO2 photolysis frequencies in street canyons

    NASA Astrophysics Data System (ADS)

    Koepke, P.; Garhammer, M.; Hess, M.; Roeth, E.-P.

    2010-05-01

    Photolysis frequencies for NO2 are modeled for the conditions in urban streets, which are taken into account as canyons with variable height and width. The effect of a street canyon is presented with absolute values and as a ratio RJ of the photolysis frequency within the street against those with free horizon, which allows further use of the existing photolysis parameterizations. Values are presented for variable solar elevation and azimuth angles, varying atmospheric conditions and different street properties. The NO2 photolysis frequency in the street, averaged over atmospheric conditions and street orientation, is reduced to less than 20% for narrow streets, to about 40% for typical urban streets, and only to about 80% for garden streets, each with about ±5% uncertainty. A parameterization of RJ with the global solar irradiance is given for values that are averaged over the meteorological conditions and the street orientation.

  8. Collecting Solar Energy. Solar Energy Education Project.

    ERIC Educational Resources Information Center

    O'Brien, Alexander

    This solar energy learning module for use with junior high school students offers a list of activities, a pre-post test, job titles, basic solar energy vocabulary, and diagrams of solar energy collectors and installations. The purpose is to familiarize students with applications of solar energy and titles of jobs where this knowledge could be…

  9. Solar Impulse's Solar-Powered Plane

    ScienceCinema

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2016-07-12

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  10. Solar Impulse's Solar-Powered Plane

    SciTech Connect

    Moniz, Ernest; Piccard, Bertrand; Reicher, Dan

    2013-07-08

    Solar Impulse lands in Washington, DC at Washington Dulles International Airport as part of its journey across the United States. Secretary Ernest Moniz speaks about how advancements like those at the Department of Energy are leading the way for innovations like the solar-powered plane. Footage of the solar-powered plane courtesy of Solar Impulse.

  11. Volcanic eruptions and solar activity

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1989-01-01

    The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

  12. Properties of solar activity and ionosphere for solar cycle 25

    NASA Astrophysics Data System (ADS)

    Deminov, M. G.; Nepomnyashchaya, E. V.; Obridko, V. N.

    2016-11-01

    Based on the known forecast of solar cycle 25 amplitude ( Rz max ≈ 50), the first assessments of the shape and amplitude of this cycle in the index of solar activity F10.7 (the magnitude of solar radio flux at the 10.7 cm wavelength) are given. It has been found that ( F10.7)max ≈ 115, which means that it is the lowest solar cycle ever encountered in the history of regular ionospheric measurements. For this reason, many ionospheric parameters for cycle 25, including the F2-layer peak height and critical frequency ( hmF2 and foF2), will be extremely low. For example, at middle latitudes, typical foF2 values will not exceed 8-10 MHz, which makes ionospheric heating ineffective in the area of upper hybrid resonance at frequencies higher than 10 MHz. The density of the atmosphere will also be extremely low, which significantly extends the lifetime of low-orbit satellites. The probability of F-spread will be increased, especially during night hours.

  13. Solar oscillations and the equation of state

    NASA Technical Reports Server (NTRS)

    Christensen-Dalsgaard, Jorgen; Daeppen, Werner

    1992-01-01

    The dependence of frequencies of solar oscillations on the thermodynamic state of the sun is considered. On the basis of an analysis of the equations of stellar structure, as well as the relevant aspects of the properties of the oscillations, it is argued that in the convection zone, information about the equation of state which is relatively unaffected by other uncertainties in the physics of the solar interior can be isolated. The different treatments that have been employed to describe the thermodynamics of stellar plasmas are reviewed. Through application of several of these treatments to the computation of models of the solar envelope, it is demonstrated that the sensitivity of the observed frequencies is in fact sufficient to distinguish even quite subtle features of the physics of solar matter.

  14. Preferred frequencies for SETI observations

    NASA Astrophysics Data System (ADS)

    Zuckerman, B.

    1983-10-01

    The proper radio bands for observing and transmitting signals to and from other star systems in a search for extraterrestrial intelligence. It is assumed that other civilizations will have developed the energies and other resources of their solar systems, and that they will use electromagnetic radiation as a communications medium. The sizes of the space based antennas that other civilizations might have built are discussed in terms of the resulting interferometers, the possible wavelengths used, and the technological bases assumed. It is suggested that transmissions might be most effective if confined to a few microns bandwidth to which the galaxy is largely transparent. However, no universal, 'magic' frequency can presently be identified, although nondirectional emissions may congregate around the 'water hole' of radio frequencies in the universe.

  15. The SSRT in the 23rd Cycle of Solar Activity

    NASA Astrophysics Data System (ADS)

    Zandanov, V. G.; Altyntsev, A. T.; Lesovoi, S. V.

    1999-12-01

    We present a sketch of the project to upgrade the Siberian Solar Radio Telescope. We suggest expanding the spectral range of receiving frequencies from a single frequency (5.7~GHz) to five frequencies and to considerably improve the sensitivity of instrument.

  16. MEASUREMENTS OF RAPID DENSITY FLUCTUATIONS IN THE SOLAR WIND

    SciTech Connect

    Malaspina, D. M.; Ergun, R. E.; Kellogg, P. J.; Bale, S. D.

    2010-03-01

    The power spectrum of density fluctuations in the solar wind is inferred by tracking small timescale changes in the electron plasma frequency during periods of strong Langmuir wave activity. STEREO electric field waveform data are used to produce time profiles of plasma density from which the density power spectrum is derived. The power spectra obtained by this method extend the observed frequency range by an order of magnitude while remaining consistent with previous results near a few Hertz. Density power spectral indices are found to be organized by the angle between the local magnetic field and the solar wind direction, indicating significant anisotropy in solar wind high-frequency density turbulence.

  17. Solar-geophysical data number 494, October 1985, Part 2: (Comprehensive reports). Data for April 1985, January-June 1984 and miscellanea

    NASA Technical Reports Server (NTRS)

    Coffey, H. E.

    1985-01-01

    Contents include: detailed index for 1985; data for April 1985 (Meudon carte synoptique, solar radio bursts at fixed frequencies, solar X-ray radiation form GOES satellite, mass ejections from the sun, active prominences and filaments); data for January to June 1984 (solar flares January 1984, solar flares February 1984, solar flares March l984, solar flares April 1984, solar flares May 1984, solar flares June 1984, and number of flates August 1966 to June 1984); and miscellaneous data (interplanetary solar wind July 1984 to March 1985, errata solar X-rays event list January 1985).

  18. Low-Frequency Waves in Space Plasmas

    NASA Astrophysics Data System (ADS)

    Keiling, Andreas; Lee, Dong-Hun; Nakariakov, Valery

    2016-02-01

    Low-frequency waves in space plasmas have been studied for several decades, and our knowledge gain has been incremental with several paradigm-changing leaps forward. In our solar system, such waves occur in the ionospheres and magnetospheres of planets, and around our Moon. They occur in the solar wind, and more recently, they have been confirmed in the Sun's atmosphere as well. The goal of wave research is to understand their generation, their propagation, and their interaction with the surrounding plasma. Low-frequency Waves in Space Plasmas presents a concise and authoritative up-to-date look on where wave research stands: What have we learned in the last decade? What are unanswered questions? While in the past waves in different astrophysical plasmas have been largely treated in separate books, the unique feature of this monograph is that it covers waves in many plasma regions, including: Waves in geospace, including ionosphere and magnetosphere Waves in planetary magnetospheres Waves at the Moon Waves in the solar wind Waves in the solar atmosphere Because of the breadth of topics covered, this volume should appeal to a broad community of space scientists and students, and it should also be of interest to astronomers/astrophysicists who are studying space plasmas beyond our Solar System.

  19. An astro-comb calibrated solar telescope to study solar activity and search for the radial velocity signature of Venus

    NASA Astrophysics Data System (ADS)

    Phillips, David; HARPS-N Collaboration

    2017-01-01

    We recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope, which is calibrated with a laser frequency comb calibrator optimized for calibrating high resolution spectrographs and referred to as an astro-comb. We are using the solar telescope to characterize the effects of stellar (solar) RV jitter due to activity on the solar surface over the course of many hours every clear day. With the help of solar satellites such as the Solar Dynamics Observatory (SDO), we are characterizing the correlation between observed RV and detailed imaging of the solar photosphere. We plan to use these tools to mitigate the effects of stellar jitter with the goal of the detection of Venus from its solar RV signature, thus showing the potential of the RV technique to detect true Earth-twins.

  20. Solar rotation.

    NASA Astrophysics Data System (ADS)

    Dziembowski, W.

    Sunspot observations made by Johannes Hevelius in 1642 - 1644 are the first ones providing significant information about the solar differential rotation. In modern astronomy the determination of the rotation rate is done in a routine way by measuring positions of various structures on the solar surface as well as by studying the Doppler shifts of spectral lines. In recent years a progress in helioseismology enabled determination of the rotation rate in the layers inaccessible for direct observations. There are still uncertainties concerning, especially, the temporal variations of the rotation rate and its behaviour in the radiative interior. We are far from understanding the observations. Theoretical works have not yet resulted in a satisfactory model for the angular momentum transport in the convective zone.

  1. Solar Flares

    NASA Technical Reports Server (NTRS)

    Savage, Sabrina

    2013-01-01

    Because the Earth resides in the atmosphere of our nearest stellar neighbor, events occurring on the Sun's surface directly affect us by interfering with satellite operations and communications, astronaut safety, and, in extreme circumstances, power grid stability. Solar flares, the most energetic events in our solar system, are a substantial source of hazardous space weather affecting our increasingly technology-dependent society. While flares have been observed using ground-based telescopes for over 150 years, modern space-bourne observatories have provided nearly continuous multi-wavelength flare coverage that cannot be obtained from the ground. We can now probe the origins and evolution of flares by tracking particle acceleration, changes in ionized plasma, and the reorganization of magnetic fields. I will walk through our current understanding of why flares occur and how they affect the Earth and also show several examples of these fantastic explosions.

  2. Solar Interior

    NASA Astrophysics Data System (ADS)

    Zahn, J.; Murdin, P.

    2000-11-01

    The interior of the Sun is hidden from our sight, because it is opaque to electromagnetic waves: the radiation we receive from it on Earth is emitted in the outermost layers. Our knowledge of the solar interior is based solely on theoretical models which are built with some assumptions about the physical conditions and processes that are likely to prevail there, and on helioseismology, a very pow...

  3. Solar collectors

    SciTech Connect

    Uroshevich, M.

    1981-09-22

    The disclosure illustrates a solar collector of the focusing type comprising a trough like element with an interior reflective surface that faces a main reflector of the collector. A tubular receiver providing a passage for heat transfer fluid is positioned in the trough like element generally along the focal line of the main reflector. A flat glass plate covers the trough along a perimeter seal so that subatmospheric conditions may be maintained within the trough like element to minimize convection heat losses.

  4. Solar cooker

    SciTech Connect

    Zwach, D.M.

    1987-09-29

    A solar unit is described comprising a solar oven having an open end. A generally concave parabolic main reflector is joined to the oven to move therewith and reflect solar radiation away from the oven. The main reflector has a central opening to the oven open end, a generally parabolic convex secondary reflector for reflecting the radiation from the main reflector through the central opening to the open end of the oven, means for mounting the secondary reflector on the main reflector for movement, a frame, and means for mounting the oven on the frame for adjustable movement relative to the frame. This permits adjusting the angular position relative to the earth. The last mentioned means includes means for supporting the oven including first and second pairs of pivot members that respectively have a fist pivot axis and a second pivot axis that extends perpendicular to the first pivot axis. The oven extends between each of the first pivot members and each of the second pivot members.

  5. Solar chameleons

    SciTech Connect

    Brax, Philippe

    2010-08-15

    We analyze the creation of chameleons deep inside the Sun (R{approx}0.7R{sub sun}) and their subsequent conversion to photons near the magnetized surface of the Sun. We find that the spectrum of the regenerated photons lies in the soft x-ray region, hence addressing the solar corona problem. Moreover, these back-converted photons originating from chameleons have an intrinsic difference with regenerated photons from axions: their relative polarizations are mutually orthogonal before Compton interacting with the surrounding plasma. Depending on the photon-chameleon coupling and working in the strong coupling regime of the chameleons to matter, we find that the induced photon flux, when regenerated resonantly with the surrounding plasma, coincides with the solar flux within the soft x-ray energy range. Moreover, using the soft x-ray solar flux as a prior, we find that with a strong enough photon-chameleon coupling, the chameleons emitted by the Sun could lead to a regenerated photon flux in the CAST magnetic pipes, which could be within the reach of CAST with upgraded detector performance. Then, axion helioscopes have thus the potential to detect and identify particle candidates for the ubiquitous dark energy in the Universe.

  6. Nanostructured Solar Cells.

    PubMed

    Chen, Guanying; Ning, Zhijun; Ågren, Hans

    2016-08-09

    We are glad to announce the Special Issue "Nanostructured Solar Cells", published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs.

  7. Solar Sail Spaceflight Simulation

    NASA Technical Reports Server (NTRS)

    Lisano, Michael; Evans, James; Ellis, Jordan; Schimmels, John; Roberts, Timothy; Rios-Reyes, Leonel; Scheeres, Daniel; Bladt, Jeff; Lawrence, Dale; Piggott, Scott

    2007-01-01

    The Solar Sail Spaceflight Simulation Software (S5) toolkit provides solar-sail designers with an integrated environment for designing optimal solar-sail trajectories, and then studying the attitude dynamics/control, navigation, and trajectory control/correction of sails during realistic mission simulations. Unique features include a high-fidelity solar radiation pressure model suitable for arbitrarily-shaped solar sails, a solar-sail trajectory optimizer, capability to develop solar-sail navigation filter simulations, solar-sail attitude control models, and solar-sail high-fidelity force models.

  8. Solar physics at APL.

    NASA Astrophysics Data System (ADS)

    Rust, D. M.

    1999-12-01

    Solar reserach at APL aims to understand the fundamental physics that govern solar activity. The tools are telescopes, models, and interplanetary sampling of solar ejecta. The work is relevant to APL's mission because solar energetic protons disable satellites and endanger astronauts. Solar activity also causes geomagnetic storms, which can lead to communications disruptions, electric power network problems, satellite orbit shifts and, sometimes, satellite failure. Predicting storm conditions requires understanding solar magnetism and its fluctuations. APL scientists have made major contributions to solar activity research and have taken the lead in developing a variety of new solar research tools. They are now starting work on the Solar Terrestrial Relations Observatory, a major space mission.

  9. Nanostructured Solar Cells

    PubMed Central

    Chen, Guanying; Ning, Zhijun; Ågren, Hans

    2016-01-01

    We are glad to announce the Special Issue “Nanostructured Solar Cells”, published in Nanomaterials. This issue consists of eight articles, two communications, and one review paper, covering major important aspects of nanostructured solar cells of varying types. From fundamental physicochemical investigations to technological advances, and from single junction solar cells (silicon solar cell, dye sensitized solar cell, quantum dots sensitized solar cell, and small molecule organic solar cell) to tandem multi-junction solar cells, all aspects are included and discussed in this issue to advance the use of nanotechnology to improve the performance of solar cells with reduced fabrication costs.

  10. Solar models, neutrino experiments, and helioseismology

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Ulrich, Roger K.

    1988-01-01

    The event rates and their recognized uncertainties are calculated for 11 solar neutrino experiments using accurate solar models. These models are also used to evaluate the frequency spectrum of the p and g oscillations modes of the sun. It is shown that the discrepancy between the predicted and observed event rates in the Cl-37 and Kamiokande II experiments cannot be explained by a 'likely' fluctuation in input parameters with the best estimates and uncertainties given in the present study. It is suggested that, whatever the correct solution to the solar neutrino problem, it is unlikely to be a 'trival' error.

  11. Solar Innovator | Alta Devices

    ScienceCinema

    Mattos, Laila; Le, Minh

    2016-07-12

    Selected to participate in the Energy Department's SunShot Initiative, Alta Devices produces solar cells that convert sunlight into electricity at world record-breaking levels of efficiency. Through its innovative solar technology Alta is helping bring down the cost of solar. Learn more about the Energy Department's efforts to advance solar technology at energy.gov/solar .

  12. Solar energy collector

    DOEpatents

    Brin, Raymond L.; Pace, Thomas L.

    1978-01-01

    The invention relates to a solar energy collector comprising solar energy absorbing material within chamber having a transparent wall, solar energy being transmitted through the transparent wall, and efficiently absorbed by the absorbing material, for transfer to a heat transfer fluid. The solar energy absorbing material, of generally foraminous nature, absorbs and transmits the solar energy with improved efficiency.

  13. Solar Innovator | Alta Devices

    SciTech Connect

    Mattos, Laila; Le, Minh

    2012-01-01

    Selected to participate in the Energy Department's SunShot Initiative, Alta Devices produces solar cells that convert sunlight into electricity at world record-breaking levels of efficiency. Through its innovative solar technology Alta is helping bring down the cost of solar. Learn more about the Energy Department's efforts to advance solar technology at energy.gov/solar .

  14. Solar Sails

    NASA Technical Reports Server (NTRS)

    Young, Roy

    2006-01-01

    The Solar Sail Propulsion investment area has been one of the three highest priorities within the In-Space Propulsion Technology (ISPT) Project. In the fall of 2003, the NASA Headquarters' Science Mission Directorate provided funding and direction to mature the technology as far as possible through ground research and development from TRL 3 to 6 in three years. A group of experts from government, industry, and academia convened in Huntsville, Alabama to define technology gaps between what was needed for science missions to the inner solar system and the current state of the art in ultra1ightweight materials and gossamer structure design. This activity set the roadmap for development. The centerpiece of the development would be the ground demonstration of scalable solar sail systems including masts, sails, deployment mechanisms, and attitude control hardware and software. In addition, new materials would be subjected to anticipated space environments to quantify effects and assure mission life. Also, because solar sails are huge structures, and it is not feasible to validate the technology by ground test at full scale, a multi-discipline effort was established to develop highly reliable analytical models to serve as mission assurance evidence in future flight program decision-making. Two separate contractor teams were chosen to develop the SSP System Ground Demonstrator (SGD). After a three month conceptual mission/system design phase, the teams developed a ten meter diameter pathfinder set of hardware and subjected it to thermal vacuum tests to compare analytically predicted structural behavior with measured characteristics. This process developed manufacturing and handling techniques and refined the basic design. In 2005, both contractor teams delivered 20 meter, four quadrant sail systems to the largest thermal vacuum chamber in the world in Plum Brook, Ohio, and repeated the tests. Also demonstrated was the deployment and articulation of attitude control

  15. High-Frequency Cutoff in Type III Bursts

    NASA Astrophysics Data System (ADS)

    Stanislavsky, A. A.; Konovalenko, A. A.; Volvach, Ya. S.; Koval, A. A.

    In this article we report about a group of solar bursts with high-frequency cutoff, observed on 19 August of 2012 near 8:23 UT, simultaneously by three different radio telescopes: the Ukrainian decameter radio telescope (8-33 MHz), the French Nancay Decametric Array (10-70 MHz) and the Italian San Vito Solar Observatory of RSTN (25-180 MHz). Morphologically the bursts are very similar to the type III bursts. The solar activity is connected with the emergency of a new group of solar spots on the far side of the Sun with respect to observers on Earth. The solar bursts accompany many moderate flares over eastern limb. The refraction of the behind-limb radio bursts towards the Earth is favorable, if CMEs generate low-density cavities in solar corona.

  16. The origin of Total Solar Irradiance variability on timescales less than a day

    NASA Astrophysics Data System (ADS)

    Shapiro, Alexander; Krivova, Natalie; Schmutz, Werner; Solanki, Sami K.; Leng Yeo, Kok; Cameron, Robert; Beeck, Benjamin

    2016-07-01

    Total Solar Irradiance (TSI) varies on timescales from minutes to decades. It is generally accepted that variability on timescales of a day and longer is dominated by solar surface magnetic fields. For shorter time scales, several additional sources of variability have been proposed, including convection and oscillation. However, available simplified and highly parameterised models could not accurately explain the observed variability in high-cadence TSI records. We employed the high-cadence solar imagery from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory and the SATIRE (Spectral And Total Irradiance Reconstruction) model of solar irradiance variability to recreate the magnetic component of TSI variability. The recent 3D simulations of solar near-surface convection with MURAM code have been used to calculate the TSI variability caused by convection. This allowed us to determine the threshold timescale between TSI variability caused by the magnetic field and convection. Our model successfully replicates the TSI measurements by the PICARD/PREMOS radiometer which span the period of July 2010 to February 2014 at 2-minute cadence. Hence, we demonstrate that solar magnetism and convection can account for TSI variability at all timescale it has ever been measured (sans the 5-minute component from p-modes).

  17. Solar effects on circulation types over Europe: an analysis based on a large number of classifications

    NASA Astrophysics Data System (ADS)

    Huth, R.; Cahynová, M.; Kyselý, J.

    2010-09-01

    Recently, effects of the 11-year solar cycle on various aspects of tropospheric circulation in the Northern Hemisphere in winter have been recognized. One of our previous studies showed a significant solar effect on the frequency of synoptic types from the Hess-Brezowsky catalogue. Here, we use a large collection of varied classifications of circulation patterns, defined over central Europe, assembled within the COST733 Action "Harmonization and Applications of Weather Types Classifications for European Regions" to detect the solar effect on the frequency of synoptic types. The advantage of this multi-classification approach is that peculiarities or biases present in any single classification (catalogue) that might influence the detected solar signal are eliminated once a large ensemble of classifications is used. We divide winter months (December to March) into three groups according to the mean monthly solar activity, quantified by the solar 10.7 cm flux. The three groups correspond to the minima of the 11-year solar cycle, a moderate solar activity, and solar maxima. Within each group, frequencies of occurrence of individual circulation types are calculated. Differences in the occurrence of individual classes between solar activity groups indicate the presence of a solar activity effect on atmospheric circulation over Europe. Statistical significance of these differences is estimated by a block resampling method. An enhanced frequency under solar minima and a reduced frequency under solar maxima are observed almost exclusively for the types with easterly flow over central Europe. On the other hand, a reduced frequency under solar minima and an enhanced frequency under solar maxima are found for the types with westerly flow over central Europe. The research is supported by the Grant Agency of the Czech Academy of Sciences, project A300420805, and by the Ministry of Education, Youth, and Sports of the Czech Republic, contract OC115.

  18. Frequency noise in frequency swept fiber laser.

    PubMed

    Pedersen, Anders Tegtmeier; Rottwitt, Karsten

    2013-04-01

    This Letter presents a measurement of the spectral content of frequency shifted pulses generated by a lightwave synthesized frequency sweeper. We found that each pulse is shifted in frequency with very high accuracy. We also discovered that noise originating from light leaking through the acousto- optical modulators and forward propagating Brillouin scattering appear in the spectrum.

  19. Faint solar radio structures from decametric observations

    NASA Astrophysics Data System (ADS)

    Briand, C.; Zaslavsky, A.; Maksimovic, M.; Zarka, P.; Lecacheux, A.; Rucker, H. O.; Konovalenko, A. A.; Abranin, E. P.; Dorovsky, V. V.; Stanislavsky, A. A.; Melnik, V. N.

    2008-10-01

    Aims: Decameter radio observations of the solar corona reveal the presence of numerous faint frequency drifting emissions, similar to “solar S bursts” which are reported in the literature. We present a statistical analysis of the characteristics of these emissions and propose a mechanism to excite the Langmuir waves thought to be at the origin of these emissions. Methods: The observations were performed between 1998 and 2002 with the Digital Spectro Polarimeter (DSP) receivers operated at the UTR-2 and Nançay decameter radio telescopes in the frequency range 15-30 MHz. Our theoretical explanation is based on Vlasov-Ampère simulations. Results: Based on the frequency drift rate, three populations of structures can be identified. The largest population presents an average negative frequency drift of -0.9 MHz s-1 and a lifetime up to 11 s (median value of 2.72 s). A second population shows a very small frequency drift of -0.1 MHz s-1 and a short lifetime of about 1 s. The third population presents an average positive frequency drift of +0.95 MHz s-1 and a lifetime of up to 3 s. Also, the frequency drift as a function of frequency is consistent with the former results, which present results in higher frequency range. No specific relationship was found between the occurrence of these emissions and the solar cycle or presence of flares. Assuming that these emissions are produced by “electron clouds” propagating the solar corona, we deduce electron velocities of about 3-5 times the electron thermal velocity. As previously shown, a localized, time-dependent modulation of the electron distribution function (heating) leads to low velocity electron clouds (consistent with observations), which, in turn, can generate Langmuir waves and electromagnetic signals by nonlinear processes.

  20. High solar intensity radiometer

    NASA Technical Reports Server (NTRS)

    Jack, J. R.; Spisz, E. W.

    1972-01-01

    Silicon solar cells are used to measure visible radiant energy and radiation intensities to 20 solar constants. Future investigations are planned for up to 100 solar constants. Radiometer is small, rugged, accurate and inexpensive.

  1. Solar Neutrino Problem

    DOE R&D Accomplishments Database

    Davis, R. Jr.; Evans, J. C.; Cleveland, B. T.

    1978-04-28

    A summary of the results of the Brookhaven solar neutrino experiment is given and discussed in relation to solar model calculations. A review is given of the merits of various new solar neutrino detectors that were proposed.

  2. Solar greenhouses in Minnesota

    SciTech Connect

    Polich, M.

    1981-12-01

    After a discussion of solar greenhouse phenomena and the potential for heat collection and food production, design recommendations are provided for attached heat collecting solar sunspaces and for attached food producing solar greenhouses. Also, design of a single solar structure to maximize heat collection and food production is considered. A method of predicting the performance for attached heat collecting solar sunspaces is given in which the solar savings fraction is calculated. (LEW)

  3. Solar Electricity

    NASA Technical Reports Server (NTRS)

    1988-01-01

    ARCO Solar manufactures PV Systems tailored to a broad variety of applications. PV arrays are routinely used at remote communications installations to operate large microwave repeaters, TV and radio repeaters rural telephone, and small telemetry systems that monitor environmental conditions. Also used to power agricultural water pumping systems, to provide electricity for isolated villages and medical clinics, for corrosion protection for pipelines and bridges, to power railroad signals, air/sea navigational aids, and for many types of military systems. ARCO is now moving into large scale generation for utilities.

  4. Solar Generator

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The Vanguard I dish-Stirling module program, initiated in 1982, produced the Vanguard I module, a commercial prototype erected by the Advanco Corporation. The module, which automatically tracks the sun, combines JPL mirrored concentrator technology, an advanced Stirling Solar II engine/generator, a low cost microprocessor-controlled parabolic dish. Vanguard I has a 28% sunlight to electricity conversion efficiency. If tests continue to prove the system effective, Advanco will construct a generating plant to sell electricity to local utilities. An agreement has also been signed with McDonnell Douglas to manufacture a similar module.

  5. The Solar Chimes: Searching for Oscillations inside the Sun.

    ERIC Educational Resources Information Center

    Wentzel, Donat G.

    1991-01-01

    The importance of investigating the sun's interior is discussed. One method for probing the interiors of some pulsating stars is described. The relationship between the sun's solar oscillation frequencies and the sun's solar cycles is discussed. A project to place six instruments around the world to observe the sun's oscillations (GONG) is…

  6. Seismology and geodesy of the sun: Solar geodesy.

    PubMed

    Dicke, R H

    1981-03-01

    Measurements of the elliptical figure of the sun made in 1966 are analyzed on an hourly basis. This analysis yields an improved measure of the previously found solar distortion, rotating rigidly with a sidereal period of 12.38+/-0.10 days. It also yields a set of residùals used to search for signals due to low-frequency solar oscillations.

  7. Solar Heating and Cooling

    ERIC Educational Resources Information Center

    Duffie, John A.; Beckman, William A.

    1976-01-01

    Describes recent research that has made solar energy economically competitive with other energy sources. Includes solar energy building architecture, storage systems, and economic production data. (MLH)

  8. Solar Energy Systems

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Calibrated in kilowatt hours per square meter, the solar counter produced by Dodge Products, Inc. provides a numerical count of the solar energy that has accumulated on a surface. Solar energy sensing, measuring and recording devices in corporate solar cell technology developed by Lewis Research Center. Customers for their various devices include architects, engineers and others engaged in construction and operation of solar energy facilities; manufacturers of solar systems or solar related products, such as glare reducing windows; and solar energy planners in federal and state government agencies.

  9. Solar radiation resource assessment

    SciTech Connect

    Not Available

    1990-11-01

    The bulletin discusses the following: introduction; Why is solar radiation resource assessment important Understanding the basics; the solar radiation resource assessment project; and future activities.

  10. Amplitudes of solar-like oscillations: a new scaling relation

    NASA Astrophysics Data System (ADS)

    Kjeldsen, H.; Bedding, T. R.

    2011-05-01

    Solar-like oscillations are excited by near-surface convection and are being observed in growing numbers of stars using ground- and space-based telescopes. We have previously suggested an empirical scaling relation to predict their amplitudes. This relation has found widespread use but it predicts amplitudes in F-type stars that are higher than observed. Here we present a new scaling relation that is based on the postulate that the power in velocity fluctuations due to p-mode oscillations scales with stellar parameters in the same way as the power in velocity fluctuations due to granulation. The new relation includes a dependence on the damping rate via the mode lifetime and should be testable using observations from the CoRoT and Kepler missions. We also suggest scaling relations for the properties of the background power due to granulation and argue that both these and the amplitude relations should be applicable to red giant stars.

  11. solar spicules and jets

    NASA Astrophysics Data System (ADS)

    Tavabi, E.; Koutchmy, S.; Ajabshirizadeh, A.

    2012-06-01

    In order to clear up the origin and possibly explain some solar limb and disc spicule quasi-periodic recurrences produced by overlapping effects, we present a simulation model assuming quasi- random positions of spicules. We also allow a set number of spicules with different physical properties (such as: height, lifetime and tilt angle as shown by an individual spicule) occurring randomly. Results of simulations made with three different spatial resolutions of the corresponding frames and also for different number density of spicules, are analyzed. The wavelet time/frequency method is used to obtain the exact period of spicule visibility. Results are compared with observations of the chromosphere from i/ the Transition Region and Coronal Explorer (TRACE) filtergrams taken at 1600 angstrom, ii/ the Solar Optical Telescope (SOT) of Hinode taken in the Ca II H-line and iii/ the Sac-Peak Dunn's VTT taken in H? line. Our results suggest the need to be cautious when interpreting apparent oscillations seen in spicule image sequences when overlapping is present, i.e.; when the spatial resolution is not enough to resolve individual components of spicules.

  12. Solar skylight

    DOEpatents

    Adamson, James C.

    1984-01-01

    A reflective shutter rotates within a skylight housing in such a fashion as to control solar energy thereby providing a combination of heating, lighting, and ventilation. The skylight housing has three faces: a glazed southern face, a glazed northern face, and an open downwardly oriented face to the interior of the structure. Counter-weighted pivot arms support the shutter at either end causing the center of rotation to pass through the center of gravity. The shutter has three basic positions: In the first position, during the winter day, the shutter closes off the northern face, allowing solar energy to enter directly into the supporting structure providing heat gain and daylighting. In the second position, during the winter night, the shutter closes off the open face to the interior, providing insulation between the structure and the skylight housing. In the third position, during the non-heating season, the shutter closes off the southern face blocking unwanted heat gain but allowing diffuse northern light to penetrate for daylighting. In this last position, a means is provided for ventilating by natural convection. The apparatus can be operated either manually or by motor.

  13. Solar collector

    DOEpatents

    Wilhelm, William G.

    1982-01-01

    The field of this invention is solar collectors, and more particularly, the invention pertains to a flat plate collector that employs high performance thin films. The solar collector of this invention overcomes several problems in this field, such as excessive hardware, cost and reliability, and other prior art drawbacks outlined in the specification. In the preferred form, the apparatus features a substantially rigid planar frame (14). A thin film window (42) is bonded to one planar side of the frame. An absorber (24) of laminate construction is comprised of two thin film layers (24a, 24b) that are sealed perimetrically. The layers (24a, 24b) define a fluid-tight planar envelope (24c) of large surface area to volume through which a heat transfer fluid flows. Absorber (24) is bonded to the other planar side of the frame. The thin film construction of the absorber assures substantially full envelope wetting and thus good efficiency. The window and absorber films stress the frame adding to the overall strength of the collector.

  14. Study of SEP solar array modifications. [technology assessment

    NASA Technical Reports Server (NTRS)

    Antonides, G. J.

    1978-01-01

    The feasibility of modifying the solar electric propulsion (SEP) 66 watt/kilogram, 12.5 kilowatt solar array blanket design to incorporate ultra-low mass blanket technology and to generate conceptual design data by modifying the SEP solar array design to 17.5kW power output was performed. Five modified designs were developed, which substituted present SEP solar array design components with one or more of 50 micron thick solar cells, 75 micron cell coverglasses, and a different blanket substrate developed by GE. A parametric analysis was performed to determine the solar array mast least weight and blanket tension required to maintain a minimum natural frequency of 0.04 Hz. The solar array wing assembly weights and power outputs were calculated, and preliminary cost estimates for flight hardware development, fabrication and qualification were made for each case studied.

  15. Utility Solar Generation Valuation Methods

    SciTech Connect

    Hansen, Thomas N.; Dion, Phillip J.

    2009-06-30

    Tucson Electric Power (TEP) developed, tested and verified the results of a new and appropriate method for accurately evaluating the capacity credit of time variant solar generating sources and reviewed new methods to appropriately and fairly evaluate the value of solar generation to electric utilities. The project also reviewed general integrated approaches for adequately compensating owners of solar generation for their benefits to utilities. However, given the limited funding support and time duration of this project combined with the significant differences between utilities regarding rate structures, solar resource availability and coincidence of solar generation with peak load periods, it is well beyond the scope of this project to develop specific rate, rebate, and interconnection approaches to capture utility benefits for all possible utilities. The project developed computer software based evaluation method models to compare solar generation production data measured in very short term time increments called Sample Intervals over a typical utility Dispatch Cycle during an Evaluation Period against utility system load data. Ten second resolution generation production data from the SGSSS and actual one minute resolution TEP system load data for 2006 and 2007, along with data from the Pennington Street Garage 60 kW DC capacity solar unit installed in downtown Tucson will be applied to the model for testing and verification of the evaluation method. Data was provided by other utilities, but critical time periods of data were missing making results derived from that data inaccurate. The algorithms are based on previous analysis and review of specific 2005 and 2006 SGSSS production data. The model was built, tested and verified by in house TEP personnel. For this phase of the project, TEP communicated with, shared solar production data with and collaborated on the development of solar generation valuation tools with other utilities, including Arizona Public

  16. Solar Energy: Solar System Design Fundamentals.

    ERIC Educational Resources Information Center

    Knapp, Henry H., III

    This module on solar system design fundamentals is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy…

  17. Solar Energy: Solar and the Weather.

    ERIC Educational Resources Information Center

    Knapp, Henry H., III

    This module on solar and the weather is one of six in a series intended for use as supplements to currently available materials on solar energy and energy conservation. Together with the recommended texts and references (sources are identified), these modules provide an effective introduction to energy conservation and solar energy technologies.…

  18. The solar cycle variation of coronal mass ejections and the solar wind mass flux

    NASA Technical Reports Server (NTRS)

    Webb, David F.; Howard, Russell A.

    1994-01-01

    Coronal mass ejections (CMEs) are an important aspect of coronal physics and a potentially significant contributor to perturbations of the solar wind, such as its mass flux. Sufficient data on CMEs are now available to permit study of their longer-term occurrency patterns. Here we present the results of a study of CME occurrence rates over more than a complete 11-year solar sunspot cycle and a comparison of these rates with those of other activity related to CMEs and with the solar wind particle flux at 1 AU. The study includes an evaluation of correlations to the CME rates, which include instrument duty cycles, visibility functions, mass detection thresholds, and geometrical considerations. The main results are as follows: (1) The frequency of occurrence of CMEs tends to track the solar activity cycle in both amplitude and phase; (2) the CME rates from different instruments, when corrected for both duty cycles and visibility functions, are reasonably consistent; (3) considering only longer-term averages, no one class of solar activity is better correlated with CME rate than any other; (4) the ratio of the annualized CME to solar wind mass flux tends to track the solar cycle; and (5) near solar maximum, CMEs can provide a significant fraction (i.e., approximately equals 15%) of the average mass flux to the near-ecliptic solar wind.

  19. Solar-geophysical data number 479, August 1981. Part 2: (Comprehensive reports), data for January 1984 and August 1981 and miscellanea. Explanation of data reports issued as number 474 (supplement) February 1984

    NASA Technical Reports Server (NTRS)

    Coffey, H. E.

    1984-01-01

    Various solar physical data are presented including: data for January 1984--(solar radio bursts af fixed frequencies, solar X-ray radiation from GOES satellite, Mass ejections from the sun); data for August 1981--solar flares; Miscellaneous data--(meudon carte synoptique, solar X-ray radiation from GOES satellite).

  20. Investigation of X-ray and optical solar flare activities during solar cycles 22 and 23

    NASA Astrophysics Data System (ADS)

    Akimov, L. A.; Belkina, I. L.; Bushueva, T. P.

    2003-02-01

    Daily X-ray flare indices (XFI) for the interval from January 1986 till June 2002 were calculated. The XFI behaviour during solar cycles 22 and 23 was studied. We compare the daily XFI with the daily optical flare indices (OFI) and with the International Relative Sunspot Numbers. The energy emitted by X-ray flares during 77 months of solar cycle 22 is shown to be about five times larger than the analogous value for the present solar cycle. We revealed statistically significant maxima in power spectra of the XFI and OFI. They correspond to periods of 25.5, 36.5, 73, 116, and 150d which presumably are appropriate to characteristic frequencies of the solar flare activity. A hypothesis on an possible effect of Mercury's variable electric charge on the origin of solar flares is proposed and corresponding estimates were made.

  1. EDITORIAL Solar harvest Solar harvest

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2010-12-01

    The first observations of the photoelectric effect date back to the early 19th century from work by Alexandre Edmond Becquerel, Heinrich Hertz, Wilhelm Hallwachs and J J Thomson. The theory behind the phenomena was clarified in a seminal paper by Einstein in 1905 and became an archetypical feature of the wave-particle description of light. A different manifestation of quantised electron excitation, whereby electrons are not emitted but excited into the valence band of the material, is what we call the photoconductive effect. As well as providing an extension to theories in fundamental physics, the phenomenon has spawned a field with enormous ramifications in the energy industry through the development of solar cells. Among advances in photovoltaic technology has been the development of organic photovoltaic technology. These devices have many benefits over their inorganic counterparts, such as light-weight, flexible material properties, as well as versatile materials' synthesis and low-cost large-scale production—all highly advantageous for manufacturing. The first organic photovoltaic systems were reported over 50 years ago [1], but the potential of the field has escalated in recent years in terms of efficiency, largely through band offsetting. Since then, great progress has been made in studies for optimising the efficiency of organic solar cells, such as the work by researchers in Germany and the Netherlands, where investigations were made into the percentage composition and annealing effects on composites of poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) [2]. Hybrid devices that aim to exploit the advantages of both inorganic and organic constituents have also proven promising. One example of this is the work reported by researchers in Tunisia and France on a systematic study for optimising the composition morphology of TiO2 nanoparticles in poly(N-vinylcarbazole) (PVK), which also led to insights

  2. Solar-geophysical data number 489, May 1985. Part 2: (Comprehensive reports). Data for December 1984, March-May 1983 and miscellanea

    NASA Technical Reports Server (NTRS)

    Coffey, H. E. (Editor)

    1985-01-01

    Contents include: detailed index for 1984 to 1985; data for December 1984--(Meudon Carte Synoptique, solar radio bursts at fixed frequencies, solar X-ray radiation from GOES satellite graphs, mass ejections from the sun, active prominences and filaments, solar irradiance); and data for March, April and May 1983--(solar flares March 1983, solar flares April 1983, solar flares May 1983, number of flares August 1966 to May 1983).

  3. Solar flares

    NASA Technical Reports Server (NTRS)

    Zirin, H.

    1974-01-01

    A review of the knowledge about solar flares which has been obtained through observations from the earth and from space by various methods. High-resolution cinematography is best carried out at H-alpha wavelengths to reveal the structure, time history, and location of flares. The classification flares in H alpha according to either physical or morphological criteria is discussed. The study of flare morphology, which shows where, when, and how flares occur, is important for evaluating theories of flares. Consideration is given to studies of flares by optical spectroscopy, radio emissions, and at X-ray and XUV wavelengths. Research has shown where and possibly why flares occur, but the physics of the instability involved, of the particle acceleration, and of the heating are still not understood.

  4. Solar neutrinos.

    NASA Astrophysics Data System (ADS)

    Cremonesi, O.

    1993-12-01

    The main purpose of this paper is to review the progress made in the field of solar-neutrino physics with the results of the last-generation experiments together with the new perspectives suggested by the future projects. An elementary introduction to energy production mechanisms and stellar models is given. Neutrino properties and oscillations are discussed with particular interest in matter effects. Present experiments and future projects are reviewed. Particular attention is devoted to the compelling background and low-statistics problems. Finally, presently available results from running experiments are discussed, in the framework of the SNP. Some conclusions on the possibilities of the new proposed projects to actually slove the problem are also given.

  5. Solar collector

    DOEpatents

    Wilhelm, W.G.

    The invention pertains to a flat plate collector that employs high performance thin films. The solar collector of this invention overcomes several problems in this field, such as excessive hardware, cost and reliability, and other prior art drawbacks outlined in the specification. In the preferred form, the apparatus features a substantially rigid planar frame. A thin film window is bonded to one planar side of the frame. An absorber of laminate construction is comprised of two thin film layers that are sealed perimetrically. The layers define a fluid-tight planar envelope of large surface area to volume through which a heat transfer fluid flows. Absorber is bonded to the other planar side of the frame. The thin film construction of the absorber assures substantially full envelope wetting and thus good efficiency. The window and absorber films stress the frame adding to the overall strength of the collector.

  6. Solar pond

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Stephens, J. B. (Inventor)

    1978-01-01

    Shallow pools of liquid to collect low-temperature solar generated thermal energy are described. Narrow elongated trenches, grouped together over a wide area, are lined with a heat-absorbing black liner. The heat-absorbing liquid is kept separate from the thermal energy removing fluid by means such as clear polyethylene material. The covering for the pond may be a fluid or solid. If the covering is a fluid, fire fighting foam, continuously generated, or siloons are used to keep the surface covering clean and insulated. If the thermal energy removing fluid is a gas, a fluid insulation layer contained in a flat polyethlene tubing is used to cover the pond. The side of the tube directed towards the sun is treated to block out ultraviolet radiation and trap in infrared radiation.

  7. The solar neutrino problem.

    NASA Astrophysics Data System (ADS)

    Xu, Renxin; Luo, Xianhan

    1995-12-01

    The solar neutrino problem (SNP) is reviewed on the bases of neutrino physics, solar neutrino detection and standard solar model. It is interesting that the detected neutrino flux values of different solar neutrino detectors are lower than the values calculated by SMM in different degree. The studies on SNP in particle physics and in astrophysics are also discussed respectively.

  8. Solar heating and you

    NASA Astrophysics Data System (ADS)

    1994-08-01

    This fact sheet for use with primary school classes describes what solar collectors are and how they work, passive solar rooms, flat-plate collectors, and why one should use solar heating systems. Making a solar air heater is described step-by-step with illustrations. A resource list for both students and teachers is provided for further information.

  9. Solar Heating Equipment

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Solar Unlimited, Inc.'s suncatcher line includes a variety of solar arrays, derived from NASA's satellite program: water heating only, partial home heating, or water and whole house central heating. Solar Unlimited developed a set of vigorous requirements to avoid problems common to solar heating technologies.

  10. Toward a Solar Civilization

    ERIC Educational Resources Information Center

    Hippel, Frank von; Williams, Robert H.

    1977-01-01

    The future of solar energy is examined environmentally, socially, and economically. Coal and nuclear fission are discussed as long-range energy alternatives and U. S. regional strategies are suggested. Discussed in detail are low temperature solar heat, solar electricity, and chemical fuels from solar energy. (MA)

  11. Solar-geophysical data number 499, March 1986. Part 2: (Comprehensive reports). Data for September 1986 and miscellanea

    NASA Technical Reports Server (NTRS)

    Coffey, H. E. (Editor)

    1986-01-01

    Solar-Geophysical Data Number 499, March 1986, Part 2 (Comprehensive Reports); Data for September 1985, and Miscellanea, contains the following: Detailed index for 1985 to 1986; Data for September 1985--(Solar flares, Solar radio bursts at fixed frequencies; Solar X-ray radiation from GOES satellite; Mass ejections from the Sun; Active prominences and filaments); (Meudon carte synoptique 7 July - 26 September 1985, Solar irradiance).

  12. Solar-Geophysical Data Number 497, January 1986. Part 2: (Comprehensive reports). Data for July 1985, and miscellanea

    NASA Technical Reports Server (NTRS)

    Coffey, H. E.

    1986-01-01

    Solar-Geophysical Data Number 497, January 1986. Part 2: (Comprehensive Reports); Data for July 1985, and Miscellanea contains the following: a detailed index for 1985; data for July 1985-(solar flares, solar radio bursts at fixed frequencies, solar x-ray radiation from GOES satellite, mass ejections from the sun, active prominences and filaments); and miscellaneous data-(Meudon carte synoptique 16 April - 13 May 1985, number of solar flares August 1966 - July 1985).

  13. Frequency Comb Cooling Project

    DTIC Science & Technology

    2014-03-18

    frequency combs ). Recently the power and spectral coverage of frequency combs have grown considerably with projected 1. REPORT DATE (DD-MM-YYYY) 4. TITLE...Aug-2011 18-May-2012 Approved for Public Release; Distribution Unlimited Final report on frequency comb cooling project The views, opinions and/or... frequency combs ). Recently the power and spectral coverage of frequency combs have grown considerably with projected average powers above 10 kW. We

  14. What Can Be Interesting in the Analysis of Crowded Solar Bursts?

    NASA Astrophysics Data System (ADS)

    Stanislavsky, A. A.; Konovalenko, A. A.; Koval, A. A.; Dorovsky, V. V.; Zarka, Ph.; Rucker, H. O.

    2015-03-01

    At decameter wavelengths the radio astronomy observations reveal a wide variety of solar bursts. They are associated with solar activity manifestations such as movements of electron beams and shock waves in solar corona, flare- related events, coronal mass ejections and others. The analysis of burst features allows one to use them as probing signals which comprise useful information about solar corona parameters and their changes over time. By frequency-time measurements of different types of solar bursts occurred about the same time one can provide a comparative study of their properties, complementing the missing pieces in the complex mosaic of solar events. In this purpose we discuss features of their signal processing by the gradient filtration, as applied to quasi-periodic bursts like a zebra pattern related to Bernstein modes. The measured frequency periodicity of the bursts gives a chance to determine the magnetic field strength in upper corona around the protracted solar minimum of solar activity.

  15. Photovoltaic solar concentrator

    DOEpatents

    Nielson, Gregory N.; Cruz-Campa, Jose Luis; Okandan, Murat; Resnick, Paul J.; Sanchez, Carlos Anthony; Clews, Peggy J.; Gupta, Vipin P.

    2015-09-08

    A process including forming a photovoltaic solar cell on a substrate, the photovoltaic solar cell comprising an anchor positioned between the photovoltaic solar cell and the substrate to suspend the photovoltaic solar cell from the substrate. A surface of the photovoltaic solar cell opposite the substrate is attached to a receiving substrate. The receiving substrate may be bonded to the photovoltaic solar cell using an adhesive force or a metal connecting member. The photovoltaic solar cell is then detached from the substrate by lifting the receiving substrate having the photovoltaic solar cell attached thereto and severing the anchor connecting the photovoltaic solar cell to the substrate. Depending upon the type of receiving substrate used, the photovoltaic solar cell may be removed from the receiving substrate or remain on the receiving substrate for use in the final product.

  16. Solar Structures Program

    DTIC Science & Technology

    2015-03-27

    charge, and the regulation output section. The solar array to battery section is responsible for taking in energy from the sun through the solar ...The team sought development of a means to collect and store the solar energy in a system that would most closely emulate a flight battery array...the students the ability to see how individual solar cells charge and distribute solar energy . They were also able to see how effects of external

  17. Development of Solar Research

    NASA Astrophysics Data System (ADS)

    Wittmann, Axel D.; Wolfschmidt, Gudrun; Duerbeck, Hilmar W.

    Originally based on a workshop on “Development of Solar Research”, held in Freiburg/Breisgau, this book contains articles on megalithic structures, the Nebra sky-disk, ancient sun cults, the observation of sunspots, the photography of the sun during eclipses, eclipse maps and expeditions, solar telescopes, solar physics during the Nazi era, archives of solar observations, scientific ballooning for solar research, site-testing on the Canary Islands, as well as on international cooperation.

  18. Solar collector array

    SciTech Connect

    Hall, John Champlin; Martins, Guy Lawrence

    2015-09-06

    A method and apparatus for efficient manufacture, assembly and production of solar energy. In one aspect, the apparatus may include a number of modular solar receiver assemblies that may be separately manufactured, assembled and individually inserted into a solar collector array housing shaped to receive a plurality of solar receivers. The housing may include optical elements for focusing light onto the individual receivers, and a circuit for electrically connecting the solar receivers.

  19. Magnetic activity of seismic solar analogs

    NASA Astrophysics Data System (ADS)

    Salabert, D.; García, R. A.; Beck, P. G.

    2016-12-01

    We present our latest results on the solar-stellar connection by studying 18 solar analogs that we identified among the Kepler seismic sample tep{salabert16a}. We measured their magnetic activity properties using observations collected by the Kepler satellite and the ground-based, high-resolution HERMES spectrograph. The photospheric (S{_ph}) and chromospheric (S) magnetic activity proxies of these seismic solar analogs are compared in relation to solar activity. We show that the activity of the Sun is actually comparable to the activity of the seismic solar analogs. Furthermore, we report on the discovery of temporal variability in the acoustic frequencies of the young (1 Gyr-old) solar analog KIC 10644253 with a modulation of about 1.5 years, which agrees with the derived photospheric activity tep{salabert16b}. It could actually be the signature of the short-period modulation, or quasi-biennal oscillation, of its magnetic activity as observed in the Sun and the 1-Gyr-old solar analog HD 30495. In addition, the lithium abundance and the chromospheric activity estimated from HERMES confirms that KIC 10644253 is a young and more active star than the Sun.

  20. Photovoltaic solar concentrator module

    SciTech Connect

    Chiang, C.J.

    1991-05-16

    This invention consists of a planar photovoltaic concentrator module for producing an electrical signal from incident solar radiation which includes an electrically insulating housing having a front wall, an opposing back wall and a hollow interior. A solar cell having electrical terminals is positioned within the interior of the housing. A planar conductor is connected with a terminal of the solar cell of the same polarity. A lens forming the front wall of the housing is operable to direct solar radiation incident to the lens into the interior of the housing. A refractive optical element in contact with the solar cell and facing the lens receives the solar radiation directed into the interior of the housing by the lens and directs the solar radiation to the solar cell to cause the solar cell to generate an electrical signal. An electrically conductive planar member is positioned in the housing to rest on the housing back wall in supporting relation with the solar cell terminal of opposite polarity. The planar member is operable to dissipate heat radiated by the solar cell as the solar cell generates an electrical signal and further forms a solar cell conductor connected with the solar cell terminal to permit the electrical signal generated by the solar cell to be measured between the planar member and the conductor.

  1. An Accurate Method to Compute the Parasitic Electromagnetic Radiations of Real Solar Panels

    NASA Astrophysics Data System (ADS)

    Andreiu, G.; Panh, J.; Reineix, A.; Pelissou, P.; Girard, C.; Delannoy, P.; Romeuf, X.; Schmitt, D.

    2012-05-01

    The methodology [1] able to compute the parasitic electromagnetic (EM) radiations of a solar panel is highly improved in this paper to model real solar panels. Thus, honeycomb composite panels, triple junction solar cells and serie or shunt regulation system can now be taken into account. After a brief summary of the methodology, the improvements are detailed. Finally, some encouraging frequency and time-domain results of magnetic field emitted by a real solar panel are presented.

  2. Low-frequency heliographic observations of the quiet Sun corona

    NASA Astrophysics Data System (ADS)

    Stanislavsky, A. A.; Koval, A. A.; Konovalenko, A. A.

    2013-12-01

    We present new results of heliographic observations of quiet-Sun radio emission fulfilled by the UTR-2 radio telescope. The solar corona investigations have been made close to the last solar minimum (Cycle 23) in the late August and early September of 2010 by means of the two-dimensional heliograph within 16.5-33 MHz. Moreover, the UTR-2 radio telescope was used also as an 1-D heliograph for one-dimensional scanning of the Sun at the beginning of September 2010 as well as in short-time observational campaigns in April and August of 2012. The average values of integral flux density of the undisturbed Sun continuum emission at different frequencies have been found. Using the data, we have determined the spectral index of quiet-Sun radio emission in the range 16.5-200 MHz. It is equal to -2.1±0.1. The brightness distribution maps of outer solar corona at frequencies 20.0 MHz and 26.0 MHz have been obtained. The angular sizes of radio Sun were estimated. It is found that the solar corona at these frequencies is stretched-out along equatorial direction. The coefficient of corona ellipticity varies slightly during above period. Its mean magnitudes are equal to ≈ 0.75 and ≈ 0.73 at 20.0 MHz and 26.0 MHz, respectively. The presented results for continuum emission of solar corona conform with being ones at higher frequencies.

  3. AUTOMATIC FREQUENCY CONTROL SYSTEM

    DOEpatents

    Hansen, C.F.; Salisbury, J.D.

    1961-01-10

    A control is described for automatically matching the frequency of a resonant cavity to that of a driving oscillator. The driving oscillator is disconnected from the cavity and a secondary oscillator is actuated in which the cavity is the frequency determining element. A low frequency is mixed with the output of the driving oscillator and the resultant lower and upper sidebands are separately derived. The frequencies of the sidebands are compared with the secondary oscillator frequency. deriving a servo control signal to adjust a tuning element in the cavity and matching the cavity frequency to that of the driving oscillator. The driving oscillator may then be connected to the cavity.

  4. Solar trap

    SciTech Connect

    Lew, H.S.

    1990-01-09

    This patent describes a solar energy collecting apparatus. It comprises: a light funneling trough including two flat light reflecting surfaces disposed in a face-to-face arrangement having an oblique angle therebetween; a two dimensional Fresnel lens covering the opening of the light funneling trough at the diverging extremity thereof; a photovoltaic panel facing the two dimensional Fresnel lens disposed adjacent to the converging extremity of the light funneling trough; and at least one dual-sided light reflecting planar member disposed radially intermediate the two light reflecting surfaces. The dual-sided light reflecting planar member extending from the converging extremity of the light funneling trough towards the diverging extremity thereof and terminated at a substantial distance away from the plane including the opening of the light funneling trough. Wherein the sunlight entering the light funneling trough through the two-dimensional Fresnel lens is refracted by the two dimensional Fresnel lens and funneled by the light funneling trough towards the converging extremity of the light funneling trough and irradiates the photovoltaic panel.

  5. An investigation of solar flares and associated solar radio bursts impact on ionospheric total electron content

    NASA Astrophysics Data System (ADS)

    Tuyizere, Sarathiel

    2016-07-01

    Solar transients events such as Coronal Mass Ejections (CMEs) and solar flares represent the cause of various aspects of space weather and can impact the modern man made technological system. Such solar transients are often associated with solar radio bursts (SRBs), particularly of type II and III that , at ground level can be detected by the CALLISTO (Compact Astronomical Low-frequency Low-cost Instrument for Spectroscopy and Transportable Observatories) solar spectrometer. The present study aims at investigating solar flares and associated SRBs impact on the ionospheric total electron content (TEC). SRBs data used are dynamic spectra covering the 2014-2015 period and detected by the CALLISTO instrument that is installed at the university of Rwanda, Kigali. To investigate ionospheric impact, we use TEC data from IGS stations located at almost the same universal time zone, and correlate the observed TEC changes to the corresponding observed solar bursts events. Preliminary observations resulting from this study indicate a slight enhancement in TEC during the burst event days. The observed TEC enhancement on the burst day can be associated to increased UV and X-rays radiations and particle acceleration that are associated with SRBs events. This work is a contribution to more understanding of the geo-space impact of solar transients phenomena for modeling and prediction.

  6. An investigation of solar flares and associated solar radio bursts on ionospheric total electron content

    NASA Astrophysics Data System (ADS)

    Uwamahoro, Jean

    2016-07-01

    Solar transients events such as Coronal Mass Ejections (CMEs) and solar flares represent are the cause of various aspects of space weather and can impact the modern man made technological system. Such solar transients are often associated with solar radio bursts (SRBs), particularly of type II and III that , at ground level can be detected by the CALLISTO (Compact Astronomical Low-frequency Low-cost Instrument for Spectroscopy and Transportable Observatories) solar spectrometer. The present study aims at investigating solar flares and associated SRBs impact on the ionospheric total electron content (TEC). SRBs data used are dynamic spectra covering the 2014-2015 period and detected by the CALLISTO instrument that is installed at the university of Rwanda, Kigali. To investigate ionospheric impact, we use TEC data from IGS stations located at almost the same universal time zone, and correlate the observed TEC changes to the corresponding observed solar bursts events. Preliminary observations resulting from this study indicate a slight enhancement in TEC during the burst event days. The observed TEC enhancement on the burst day can be associated to increased UV and X-rays radiations and particle acceleration that are associated with SRBs events. This work is a contribution to more understanding of the geo-space impact of solar transients phenomena for modeling and prediction.

  7. Stability analysis of the Gravito-Electrostatic Sheath-based solar plasma equilibrium

    NASA Astrophysics Data System (ADS)

    Karmakar, P. K.; Goutam, H. P.; Lal, M.; Dwivedi, C. B.

    2016-08-01

    We present approximate solutions of non-local linear perturbational analysis for discussing the stability properties of the Gravito-Electrostatic Sheath (GES)-based solar plasma equilibrium, which is indeed non-uniform on both the bounded and unbounded scales. The relevant physical variables undergoing perturbations are the self-solar gravity, electrostatic potential and plasma flow along with plasma population density. We methodologically derive linear dispersion relation for the GES fluctuations, and solve it numerically to identify and characterize the existent possible natural normal modes. Three distinct natural normal modes are identified and named as the GES-oscillator mode, GES-wave mode and usual (classical) p-mode. In the solar wind plasma, only the p-mode survives. These modes are found to be linearly unstable in wide-range of the Jeans-normalized wavenumber, k. The local plane-wave approximation marginally limits the validity or reliability of the obtained results in certain radial- and k-domains only. The phase and group velocities, time periods of these fluctuation modes are investigated. It is interesting to note that, the oscillation time periods of these modes are 3-10 min, which match exactly with those of the observed helio-seismic waves and solar surface oscillations. The proposed GES model provides a novel physical view of the waves and oscillations of the Sun from a new perspective of plasma-wall interaction physics. Due to simplified nature of the considered GES equilibrium, it is a neonatal stage to highlight its applicability in the real Sun. The proposed GES model and subsequent fluctuation analysis need further improvements to make it more realistic.

  8. Solar Design Workbook

    SciTech Connect

    Franta, G.; Baylin, F.; Crowther, R.; Dubin, F.; Grace, A., Griffith, J.W.; Holtz, M.; Kutscher, C.; Nordham, D.; Selkowitz, S.; Villecco, M.

    1981-06-01

    This Solar Design Workbook presents solar building design applications for commercial buildir^s. The book is divided into four sections. The first section describes the variety of solar applications in buildings including conservation aspects, solar fundamentals, passive systems, active systems, daylighting, and other solar options. Solar system design evaluation techniques including considerations for building energy requirements, passive systems, active systems, and economics are presented in Section II. The third section attempts to assist the designer in the building design process for energy conservation and solar applications including options and considerations for pre-design, design, and post-design phases. The information required for the solar design proee^ has not been fully developed at this time. Therefore, Section III is incomplete, but an overview of the considerations with some of the design proces elements is presented. Section IV illustrates ease studies that utilize solar applications in the building design.

  9. Amorphous silicon solar cells

    NASA Astrophysics Data System (ADS)

    Takahashi, K.; Konagai, M.

    The fabrication, performance, and applications of a-Si solar cells are discussed, summarizing the results of recent experimental investigations and trial installations. Topics examined include the fundamental principles and design strategies of solar power installations; the characteristics of monocrystalline-Si solar cells; techniques for reducing the cost of solar cells; independent, linked, and hybrid solar power systems; proposed satellite solar power systems; and the use of solar cells in consumer appliances. Consideration is given to the history of a-Si, a-Si fabrication techniques, quality criteria for a-Si films, solar cells based on a-Si, and techniques for increasing the efficiency and lowering the cost of a-Si solar cells. Graphs, diagrams, drawings, and black-and-white and color photographs are provided.

  10. Ondvrejov solar radio WWW page

    NASA Astrophysics Data System (ADS)

    Jivrivcka, Karel; Meszarosova, Hana

    Since mid 1997 the Solar Radio Astronomy Group of the Astronomical Institute in Ondvrejov has been running a new WWW page. You can find us at the address --- http://sunkl.asu.cas.cz/radio/ --- where information about our instruments, observed frequencies, as well as about our data archive is available. The home page includes four main topics: 1. Observation & Instrumentation --- here you can find information about which instruments are currently in use, observed frequencies, time resolutions etc. Presently we use for solar radio observations three dedicated instruments: RT3 -- single frequency 3 GHz receiver with 10 ms time resolution RT4 -- radio spectrograph 2.0--4.5 GHz with 100 ms time resolution RT5 -- radio spectrograph 0.8--2.0 GHz with 100 ms time resolution The observations are run daily, while the Sun is higher then 5 degrees above the horizon. Because of the tremendous amount of data, only chosen time intervals with radio events are archived. Event Archive Info: --- here you can find information about archived data (date, time interval) as well as overall images of individual events in GIF format (the image names are at the same time hyperlinks for direct loading) sorted by date and time of observation. Gallery: --- here you can find some representative examples of spectra of solar radio events, recorded by our instruments. Anonymous FTP Server: --- enables direct FTP access to our image archive. This WWW page should give you an insight, what data are available and what the events look roughly like. The uncalibrated rough data from our archive can be processed only by special programs and are not generally free. But if you are interested in a particular event from our archive, you can contact us via e-mail address: radio@asu.cas.cz This work has been supported by the Czech Academy of Sciences through grant no.A3003707.

  11. Solar Adaptive Optics.

    PubMed

    Rimmele, Thomas R; Marino, Jose

    Adaptive optics (AO) has become an indispensable tool at ground-based solar telescopes. AO enables the ground-based observer to overcome the adverse effects of atmospheric seeing and obtain diffraction limited observations. Over the last decade adaptive optics systems have been deployed at major ground-based solar telescopes and revitalized ground-based solar astronomy. The relatively small aperture of solar telescopes and the bright source make solar AO possible for visible wavelengths where the majority of solar observations are still performed. Solar AO systems enable diffraction limited observations of the Sun for a significant fraction of the available observing time at ground-based solar telescopes, which often have a larger aperture than equivalent space based observatories, such as HINODE. New ground breaking scientific results have been achieved with solar adaptive optics and this trend continues. New large aperture telescopes are currently being deployed or are under construction. With the aid of solar AO these telescopes will obtain observations of the highly structured and dynamic solar atmosphere with unprecedented resolution. This paper reviews solar adaptive optics techniques and summarizes the recent progress in the field of solar adaptive optics. An outlook to future solar AO developments, including a discussion of Multi-Conjugate AO (MCAO) and Ground-Layer AO (GLAO) will be given.

  12. SOLARES - A new hope for solar energy

    NASA Technical Reports Server (NTRS)

    Billman, K. W.; Gilbreath, W. P.; Bowen, S. W.

    1978-01-01

    A system of orbiting reflectors, SOLARES, has been studied as a possible means of reducing the diurnal variation and enhancing the average intensity of sunlight with a space system of minimum mass and complexity. The key impact that such a system makes on the economic viability of solar farming and other solar applications is demonstrated. The system is compatible with incremental implementation and continual expansion to meet the world's power needs. Key technology, environmental, and economic issues and payoffs are identified. SOLARES appears to be economically superior to other advanced, and even competitive with conventional, energy systems and could be scaled to completely abate our fossil fuel usage for power generation. Development of the terrestrial solar conversion technique, optimized for this new artificial source of solar radiation, yet remains.

  13. Silicon Carbide Solar Cells Investigated

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Raffaelle, Ryne P.

    2001-01-01

    The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.

  14. Turbulence and wave particle interactions in solar-terrestrial plasmas

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.; Goldman, M. V.; Toomre, J.

    1985-01-01

    Activities in the following study areas are reported: (1) particle and wave processes in solar flares; (2) solar convection zone turbulence; and (3) solar radiation emission. To investigate the amplification of cyclotron maser radiation in solar flares, a radio frequency. (RF) heating model was developed for the corona surrounding the energy release site. Then nonlinear simulations of compressible convection display prominent penetration by plumes into regions of stable stratification at the base of the solar convection zone, leading to the excitation of internal gravity waves there. Lastly, linear saturation of electron-beam-driven Langmuir waves by ambient density fluctuations, nonlinear saturation by strong turbulence processes, and radiation emission mechanisms are examined. An additional section discusses solar magnetic fields and hydromagnetic waves in inhomogeneous media, and the effect of magnetic fields on stellar oscillation.

  15. Solar synthetic fuel production

    NASA Astrophysics Data System (ADS)

    Bilgen, E.; Bilgen, C.

    In this paper, a thermodynamic study is presented on solar hydrogen production using concentrated solar energy. In the first part, the direct decomposition process has been studied. The temperature requirements at various partial pressures of H2O, H2 and H yields, thermal efficiency and separation of products are discussed. In the second part, using consistent costing bases, the cost of hydrogen is estimated for solar-direct decomposition process and solar-electrolysis process. It has been found that the solar-direct decomposition process concept provides hydrogen costs in the range of $22/GJ which are lower by $15-$26 than those provided by a solar electrolysis process.

  16. Solar Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Gerrish, Harold P., Jr.

    2003-01-01

    This paper presents viewgraphs on Solar Thermal Propulsion (STP). Some of the topics include: 1) Ways to use Solar Energy for Propulsion; 2) Solar (fusion) Energy; 3) Operation in Orbit; 4) Propulsion Concepts; 5) Critical Equations; 6) Power Efficiency; 7) Major STP Projects; 8) Types of STP Engines; 9) Solar Thermal Propulsion Direct Gain Assembly; 10) Specific Impulse; 11) Thrust; 12) Temperature Distribution; 13) Pressure Loss; 14) Transient Startup; 15) Axial Heat Input; 16) Direct Gain Engine Design; 17) Direct Gain Engine Fabrication; 18) Solar Thermal Propulsion Direct Gain Components; 19) Solar Thermal Test Facility; and 20) Checkout Results.

  17. Solarization of heliostat glasses

    NASA Astrophysics Data System (ADS)

    Vitko, J., Jr.; Shelby, J. E.

    1980-09-01

    A solar-induced decrease in Fe(2+) absorption was observed in heliostat glasses from the solar furnace at Odeillo, France. This decrease occurs throughout the sample and is of sufficient magnitude to result in an increase of 2.5% in solar transmittance in a period of nine years. Optical and ESR studies did not detect a corresponding increase in Fe(3+) concentration. The effect of these results on a microscopic model for the observed solarization is discussed. Solar simulation studies produced changes of magnitude and sign similar to those observed in the field exposed samples, and offer attractive means for screening samples for solarization tendencies.

  18. Solar prominences

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Aulanier, Guillaume; Török, Tibor

    2009-03-01

    Solar filaments (or prominences) are magnetic structures in the corona. They can be represented by twisted flux ropes in a bipolar magnetic environment. In such models, the dipped field lines of the flux rope carry the filament material and parasitic polarities in the filament channel are responsible for the existence of the lateral feet of prominences. Very simple laws do exist for the chirality of filaments, the so-called “filament chirality rules”: commonly dextral/sinistral filaments corresponding to left- (resp. right) hand magnetic twists are in the North/South hemisphere. Combining these rules with 3D weakly twisted flux tube models, the sign of the magnetic helicity in several filaments were identified. These rules were also applied to the 180° disambiguation of the direction of the photospheric transverse magnetic field around filaments using THEMIS vector magnetograph data (López Ariste et al. 2006). Consequently, an unprecedented evidence of horizontal magnetic support in filament feet has been observed, as predicted by former magnetostatic and recent MHD models. The second part of this review concerns the role of emerging flux in the vicinity of filament channels. It has been suggested that magnetic reconnection between the emerging flux and the pre-existing coronal field can trigger filament eruptions and CMEs. For a particular event, observed with Hinode/XRT, we observe signatures of such a reconnection, but no eruption of the filament. We present a 3D numerical simulation of emerging flux in the vicinity of a flux rope which was performed to reproduce this event and we briefly discuss, based on the simulation results, why the filament did not erupt.

  19. DDC Descriptor Frequencies.

    ERIC Educational Resources Information Center

    Klingbiel, Paul H.; Jacobs, Charles R.

    This report summarizes the frequency of use of the 7144 descriptors used for indexing technical reports in the Defense Documentation Center (DDC) collection. The descriptors are arranged alphabetically in the first section and by frequency in the second section. The frequency data cover about 427,000 AD documents spanning the interval from March…

  20. Eastern Frequency Response Study

    SciTech Connect

    Miller, N.W.; Shao, M.; Pajic, S.; D'Aquila, R.

    2013-05-01

    This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

  1. Making Sense of Frequency.

    ERIC Educational Resources Information Center

    Larsen-Freeman, Diane

    2002-01-01

    Responds to Ellis (2002), which focuses on frequency in language processing, language use, and language acquisition. Contextualizes the frequency factor in terms of the evolution of second language acquisition (SLA) research. Suggests that although relevant and important, the frequency factor requires greater definition and qualification.…

  2. Frequency Response Tool

    SciTech Connect

    Etingov, Pavel; Chassin, PNNL David; Zhang, PNNL Yu; PNNL,

    2014-03-13

    According to the North American Electric Reliability Corporation (NERC) definition: “Frequency response is a measure of an Interconnection’s ability to stabilize frequency immediately following the sudden loss of generation or load, and is a critical component of the reliable operation of the Bulk-Power System, particularly during disturbances and recoveries. Failure to maintain frequency can disrupt the operation of equipment and initiate disconnection of power plant equipment to prevent it from being damaged, which could lead to wide-spread blackouts.” Frequency Response Tool automates the power system frequency response analysis process. The tool performs initial estimation of the system frequency parameters (initial frequency, minimum frequency, settling point). User can visually inspect and adjust these parameters. The tool also calculates the frequency response performance metrics of the system, archives the historic events and baselines the system performance. Frequency response performance characteristics of the system are calculated using phasor measurement unit (PMU) information. Methodology of the frequency response performance assessment implemented in the tool complies with the NERC Frequency response standard.

  3. Biggest Solar Flare on Record

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Earth is now 10,000 times greater than normal. The increase of particles at this energy level still poses no appreciable hazard to air travelers, astronauts or satellites, and the NOAA SEC rates this radiation storm as a moderate S2 to S3, on a scale that goes to S5. Monday's solar flare produced an R4 radio blackout on the sunlit side of the Earth. An R4 blackout, rated by the NOAA SEC, is second to the most severe R5 classification. The classification measures the disruption in radio communications. X-ray and ultraviolet light from the flare changed the structure of the Earth's electrically charged upper atmosphere (ionosphere). This affected radio communication frequencies that either pass through the ionosphere to satellites or are reflected by it to traverse the globe. The SOHO mission is being conducted collaboratively between the European Space Agency and NASA. Images courtesy SOHO Project, NASA's Goddard Space Flight Center

  4. Frequency spectra of short-period variations of cosmic ray

    NASA Technical Reports Server (NTRS)

    Antonova, V. P.; Zusmanovich, A. G.

    1985-01-01

    Frequency spectra for different periods of solar activity were calculated by 5-minutes data of a neutron super-monitor, (altitude 3340 m, cutoff rigidity is 6, 7 GV, counting rate is about 4.5.10 per hour). It was shown that shifting of the spectrum power from low-frequency range to high-frequency range takes place from minimum to maximum of the solar activity. It was reliably distinguished the peak with 160-minutes period coincided with the period of the Sun's atmosphere oscillation and some types of geomagnetic pulsation by the method of accumulation of the frequency spectra. It was conducted the comparison of cosmic ray spectra with spectra of geomagnetic field for the same point of the registration and at the same period.

  5. Seismology and geodesy of the sun: Low-frequency oscillations.

    PubMed

    Dicke, R H

    1981-04-01

    The hourly averages of the solar ellipticity measured from June 13 to Sept. 17, 1966, are analyzed for indications of solar oscillations with periods in excess of 2 hr nu < 0.5 hr(-1). Nothing significant is found for frequencies nu > 0.1 hr(-1) but for lower frequencies the power spectrum shows a very complex structure containing about 20 strong narrow peaks. The complexity is illusionary. The signal apparently consists of only two frequencies. The complexity is due to aliasing by the window function with its basic 24-hr period, with many observational days missing, and with different numbers of hourly averages for the various observational days. Both signal frequencies are apparently due to odd-degree spherical harmonic oscillations of the sun.

  6. Seismology and geodesy of the sun: low-frequency oscillations

    SciTech Connect

    Dicke, R.H.

    1981-04-01

    The hourly averages of the solar ellipticity measured from June 13 to September 17, 1966, are analyzed for indications of solar oscillations with periods in excess of 2 h ..nu.. < 0.5 h/sup -1/. Nothing significant is found for frequencies ..nu.. > 0.1 hr/sup -1/ but for lower frequencies the power spectrum shows a very complex structure containing about 20 strong narrow peaks. The complexity is illusionary. The signal apparently consists of only two frequencies. The complexity is due to aliasing by the window function with its basic 24-h period, with many observational days missing, and with different numbers of hourly averages for the various observational days. Both signal frequencies are apparently due to odd-degree spherical harmonic oscillations of the sun.

  7. The Korean Solar Radio Burst Locator (KSRBL)

    NASA Astrophysics Data System (ADS)

    Dou, Yujiang; Gary, Dale E.; Liu, Zhiwei; Nita, Gelu M.; Bong, Su-Chan; Cho, Kyung-Suk; Park, Young-Deuk; Moon, Yong-Jae

    2009-05-01

    This paper describes the design and operation of the Korean Solar Radio Burst Locator (KSRBL). The KSRBL is a radio spectrometer designed to observe solar decimeter and microwave bursts over a wide band (0.245–18 GHz) as well as to detect the burst locations without interferometry or mechanical sweeping. As a prototype, it is temporarily observing at the Owens Valley Radio Observatory (OVRO), California, USA, and after commissioning will be operated at the Korea Astronomy and Space Science Institute (KASI), Daejeon, Republic of Korea. The control system can agilely choose four 500 MHz intermediate frequency (IF) bands (2 GHz instantaneous bandwidth) from the entire 0.245–18 GHz band, with a standard time resolution of 100 ms, although higher time resolution is possible subject to data-rate constraints. To cover the entire band requires 10 tunings, which are therefore completed in 1 s. Each 500 MHz band is sampled at a 1 GS s-1 (gigasample per second) rate, and 4096 time samples are Fast Fourier transformed (FFT) to 2048 subchannels for a frequency resolution of 0.24 MHz. To cover the entire range also requires two different feeds, a dual-frequency Yagi centered at 245 and 410 MHz, and a broadband spiral feed covering 0.5–18 GHz. The dynamic range is 35 dB over the 0.5–18 GHz band, and 55 dB in the 245 and 410 MHz bands, set by using switchable attenuators in steps of 5 dB. Each 500 MHz IF has a further 63 dB of settable analog attenuation. The characteristics of the spiral feed provide the ability to locate flaring sources on the Sun to typically 2‧. The KSRBL will provide a broadband view of solar bursts for the purposes of studying solar activity for basic research, and for monitoring solar activity as the source of Space Weather and solar-terrestrial effects.

  8. Solar Rotational Periodicities and the Semiannual Variation in the Solar Wind, Radiation Belt, and Aurora

    NASA Technical Reports Server (NTRS)

    Emery, Barbara A.; Richardson, Ian G.; Evans, David S.; Rich, Frederick J.; Wilson, Gordon R.

    2011-01-01

    The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from S to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005 -2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (approx.1980, approx.1990, and approx. 2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995-1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27 -day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the > 2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods

  9. Frequency selective infrared sensors

    DOEpatents

    Davids, Paul; Peters, David W

    2013-05-28

    A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

  10. Frequency selective infrared sensors

    SciTech Connect

    Davids, Paul; Peters, David W

    2014-11-25

    A frequency selective infrared (IR) photodetector having a predetermined frequency band. The exemplary frequency selective photodetector includes: a dielectric IR absorber having a first surface and a second surface substantially parallel to the first surface; an electrode electrically coupled to the first surface of the dielectric IR absorber; and a frequency selective surface plasmonic (FSSP) structure formed on the second surface of the dielectric IR absorber. The FSSP structure is designed to selectively transmit radiation in the predetermined frequency band that is incident on the FSSP structure substantially independent of the angle of incidence of the incident radiation on the FSSP structure.

  11. Harmonic Frequency Lowering

    PubMed Central

    Kirchberger, Martin

    2016-01-01

    A novel algorithm for frequency lowering in music was developed and experimentally tested in hearing-impaired listeners. Harmonic frequency lowering (HFL) combines frequency transposition and frequency compression to preserve the harmonic content of music stimuli. Listeners were asked to make judgments regarding detail and sound quality in music stimuli. Stimuli were presented under different signal processing conditions: original, low-pass filtered, HFL, and nonlinear frequency compressed. Results showed that participants reported perceiving the most detail in the HFL condition. In addition, there was no difference in sound quality across conditions. PMID:26834122

  12. Sub-photosphere to Solar Atmosphere Connection

    NASA Astrophysics Data System (ADS)

    Komm, Rudolf; De Moortel, Ineke; Fan, Yuhong; Ilonidis, Stathis; Steiner, Oskar

    2015-12-01

    Magnetic fields extend from the solar interior through the atmosphere. The formation and evolution of active regions can be studied by measuring subsurface flows with local helioseismology. The emergence of magnetic flux from the solar convection zone is associated with acoustic perturbation signatures. In near-surface layers, the average dynamics can be determined for emerging regions. MHD simulations of the emergence of a twisted flux tube show how magnetic twist and free energy are transported from the interior into the corona and the dynamic signatures associated with such transport in the photospheric and sub-photospheric layers. The subsurface twisted flux tube does not emerge into the corona as a whole in emerging active regions. Shear flows at the polarity inversion line and coherent vortical motions in the subsurface flux tubes are the major means by which twist is transported into the corona, leading to the formation of sigmoid-shaped coronal magnetic fields capable of driving solar eruptions. The transport of twist can be followed from the interior by using the kinetic helicity of subsurface flows as a proxy of magnetic helicity; this quantity holds great promise for improving the understanding of eruptive phenomena. Waves are not only vital for studying the link between the solar interior and the surface but for linking the photosphere with the corona as well. Acoustic waves that propagate from the surface into the magnetically structured, dynamic atmosphere undergo mode conversion and refraction. These effects enable atmospheric seismology to determine the topography of magnetic canopies in the solar atmosphere. Inclined magnetic fields lower the cut-off frequency so that low frequency waves can leak into the outer atmosphere. Recent high resolution, high cadence observations of waves and oscillations in the solar atmosphere, have lead to a renewed interest in the potential role of waves as a heating mechanism. In light of their potential contribution

  13. Preliminary prediction of the 25-thTH solar cycle parameters

    NASA Astrophysics Data System (ADS)

    Pishkalo, M.

    2014-12-01

    Solar activity varies with a period of about 11 years. The solar activity variations cause changes in the interplanetary and near-Earth space. The whole space weather is mainly controlled by the solar activity. Changes in space weather affect the operation of space-borne and ground-based technological systems such as manned space flights, aero-navigation and space navigation, radars, high-frequency radio communication, GPS navigation, ground power lines. The solar activity variations influence living organisms and the climate on Earth. That is why it is important to know the level of solar activity in a solar cycle in advance. Current solar activity is near the maximum of solar cycle 24. Maximal monthly sunspot number was 102.8 in February 2014 and smoothed one was 75.4 in November 2013 (preliminary). Taking it into account and using correlation relations and regression equations from (Pishkalo, 2014: Solar Phys., vol. 289, 1815) we can estimate duration of solar cycle 24 and then predict parameters of solar cycle 25. Precursors in our calculations are the estimated duration of solar cycle 24 and sunspot number at the end of the cycle. We found that minimum and maximum of solar cycle 25 in monthly sunspot numbers will amount to 5 in April–June of 2020 and 105–110 in October–December of 2024, respectively. Solar cycle 25 will be stronger than the current cycle 24. No very deep drop in solar activity similar to Dalton or Maunder minimums was predicted.

  14. Low Radio Frequency Picosatellite Missions

    NASA Astrophysics Data System (ADS)

    Jones, Dayton L.

    2014-06-01

    The dramatic advances in cubesat and other picosatellite capabilities are opening the door for scientifically important observations at low radio frequencies. Because simple antennas are effective at low frequencies, and receiver technology allows low mass and low power instruments, these observations are an ideal match for very small spacecraft. A workshop on cubesat missions for low frequency radio astronomy was held at the Kiss Institute for Space Sciences, Caltech, to explore mission concepts involving one up to hundreds of picosatellites. One result from this workshop was that there are opportunities for viable missions throughout this large range. For example, the sky-integrated spectral signature of highly redshifted neutral hydrogen from the dark ages and cosmic dawn epochs can be measured by a single antenna on a single spacecraft. There are challenging issues of calibration, foreground removal, and RF interference that need to be solved, but the basic concept is appealingly simple. At the other extreme, imaging of angular structure in the high-redshift hydrogen signal will require an interferometer array with a very large number of antennas. In this case the primary requirement is a sufficiently low individual spacecraft mass that hundreds can be launched affordably. The technical challenges for large arrays are long-term relative station keeping and high downlink data rates. Missions using several to a few tens of picosatellites can image and track bright sources such as solar and planetary radio bursts, and will provide essential validation of technologies needed for much larger arrays.This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  15. GPM Solar Array Gravity Negated Deployment Testing

    NASA Technical Reports Server (NTRS)

    Penn, Jonathan; Johnson, Chris; Lewis, Jesse; Dear, Trevin; Stewart, Alphonso

    2014-01-01

    NASA Goddard Space Flight Center (GSFC) successfully developed a g-negation support system for use on the solar arrays of the Global Precipitation Measurement (GPM) Satellite. This system provides full deployment capability at the subsystem and observatory levels. In addition, the system provides capability for deployed configuration first mode frequency verification testing. The system consists of air pads, a support structure, an air supply, and support tables. The g-negation support system was used to support all deployment activities for flight solar array deployment testing.

  16. Radio frequency spectrum management

    NASA Astrophysics Data System (ADS)

    Sujdak, E. J., Jr.

    1980-03-01

    This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC), and the Department of Defense (DoD). Based on an analysis of Department of Defense frequency assignment procedures, recommendations are given concerning decentralizing military frequency assignment by delegating broader authority to unified commanders. This proposal includes a recommendation to colocate the individual Service frequency management offices at the Washington level. This would result in reduced travel costs, lower manpower requirements, and a common tri-Service frequency management data base.

  17. Time and Frequency Activities at the JHU Applied Physics Laboratory

    DTIC Science & Technology

    2010-11-01

    mass ejections (STEREO) to the examination of the outer planets and the Kuiper Belt objects (New Horizons). This support includes providing precise...missions that span our solar system from the study of the Sun’s coronal mass ejections (STEREO) to the examination of the outer planets and the Kuiper ... Belt objects (New Horizons). This support includes providing precise time and frequency to the integration and testing of flight hardware, frequency

  18. Weak compressible magnetohydrodynamic turbulence in the solar corona.

    PubMed

    Chandran, Benjamin D G

    2005-12-31

    This Letter presents a calculation of the power spectra of weakly turbulent Alfvén waves and fast magnetosonic waves ("fast waves") in low- plasmas. It is shown that three-wave interactions transfer energy to high-frequency fast waves and, to a lesser extent, high-frequency Alfvén waves. High-frequency waves produced by MHD turbulence are a promising explanation for the anisotropic heating of minor ions in the solar corona.

  19. Solar power roof shingle

    NASA Technical Reports Server (NTRS)

    Forestieri, A. F.; Ratajczak, A. F.; Sidorak, L. G.

    1975-01-01

    Silicon solar cell module provides both all-weather protection and electrical power. Module consists of array of circular silicon solar cells bonded to fiberglass substrate roof shingle with fluorinated ethylene propylene encapsulant.

  20. Solar Neutral Particles

    NASA Video Gallery

    This animation shows a neutral solar particle's path leaving the sun, following the magnetic field lines out to the heliosheath. The solar particle hits a hydrogen atom, stealing its electron, and ...

  1. Solar Wind Five

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (Editor)

    1983-01-01

    Topics of discussion were: solar corona, MHD waves and turbulence, acceleration of the solar wind, stellar coronae and winds, long term variations, energetic particles, plasma distribution functions and waves, spatial dependences, and minor ions.

  2. Solar Thermal Rocket Propulsion

    NASA Technical Reports Server (NTRS)

    Sercel, J. C.

    1986-01-01

    Paper analyzes potential of solar thermal rockets as means of propulsion for planetary spacecraft. Solar thermal rocket uses concentrated Sunlight to heat working fluid expelled through nozzle to produce thrust.

  3. Solar Resource Assessment

    SciTech Connect

    Renne, D.; George, R.; Wilcox, S.; Stoffel, T.; Myers, D.; Heimiller, D.

    2008-02-01

    This report covers the solar resource assessment aspects of the Renewable Systems Interconnection study. The status of solar resource assessment in the United States is described, and summaries of the availability of modeled data sets are provided.

  4. The global solar dynamo

    NASA Astrophysics Data System (ADS)

    Cameron, Robert

    2016-07-01

    I will review our understanding of the solar dynamo, concentrating on how observations constrain the theoretical possibilities. Possibilities for future progress, including understanding the Sun in the solar-stellar context will be outlined.

  5. Solar Control design package

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Information used in the evaluation of design of Solar Control's solar heating and cooling system controller and the Solarstat is given. Some of the information includes system performance specifications, design data brochures, and detailed design drawings.

  6. Glory Solar Array Deployment

    NASA Video Gallery

    The Glory spacecraft uses Orbital Sciences Corporation Space Systems Group's LEOStar-1 bus design, with deployable, four-panel solar arrays. This conceptual animation reveals Glory's unique solar a...

  7. Purification of Solar Ponds

    NASA Technical Reports Server (NTRS)

    Carpenter, S.

    1985-01-01

    Flocculatory agents added to solar saltponds remove turbidity to increase solar-energy collection efficiency. Flocculating agent or bacteriocide used to remove micro-organisms sprayed onto pond from airplane and allowed to settle to bottom of pond.

  8. Rare Earth or Cosmic Zoo: Testing the Frequency of Complex Life in the Universe

    NASA Astrophysics Data System (ADS)

    Bains, W.; Schulze-Makuch, D.

    2017-02-01

    We propose how to test between two major hypotheses about the frequency of life in the universe (Rare Earth and Cosmic Zoo) using future remote sensing capabilities targeted at exoplanets and site visits of planetary bodies in our solar system.

  9. The Astronomical Low Frequency Array: A Proposed Explorer Mission for Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Jones, D.; Allen, R.; Basart, J.; Bastian, T.; Bougeret, J. L.; Dennison, B.; Desch, M.; Dwarakanath, K.; Erickson, W.; Finley, D.; Kaiser, M.; Kassim, N.; Kuiper, T.; MacDowall, R.; Mahoney, M.; Perley, R.; Preston, R.; Reiner, M.; Rodriguez, P.; Stone, R.; Unwin, S.; Weiler, K.; Woan, G.; Woo, R.

    1999-01-01

    A radio interferometer array in space providing high dynamic range images with unprecedented angular resolution over the broad frequency range from 0.030 - 30 MHz will open new vistas in solar, terrestial, galactic, and extragalactic astrophysics.

  10. Initial Observations of Solar Bursts with the Expanded Owens Valley Solar Array

    NASA Astrophysics Data System (ADS)

    Gary, Dale E.; Kuroda, Natsuha; Fleishman, Gregory; Nita, Gelu M.; White, Stephen; Hurford, Gordon; McTiernan, James

    2015-04-01

    The Expanded Owens Valley Solar Array (EOVSA) is a newly expanded and upgraded, solar-dedicated radio array consisting of 13 antennas equipped with receivers designed to cover the 1-18 GHz frequency range. Beginning in the fall of 2014, it began taking data on four antennas in total power mode, and observed a number of solar flares ranging from the X3.1 flare of 2014 Oct 24 to small events of low C-class, with 1-s time resolution at more than 300 frequencies in the range 2.5-18 GHz. The array is now (Feb. 2015) operating with 8 antennas in both total power and interferometry mode, and is rapidly being commissioned for full operation with all 13 antennas. Here we present some initial observations with the array, emphasizing the remarkable temporal and spectral resolution of the instrument, together with joint RHESSI hard X-ray and SDO EUV observations.

  11. Solar driven climate changes recorded in Holocene alpine speleothems

    NASA Astrophysics Data System (ADS)

    Frisia, S.; Borsato, A.; Preto, N.; McDermott, F.

    2003-04-01

    Inter-annual variations in the growth rate of three annually laminated speleothems from Grotta di Ernesto, an alpine cave located at 1160 m a.s.l. in northern Italy, reveal significant periodicities at ca. 1/11 and 1/22 cycles/yr, related to changes in solar irradiance. Additional frequency components may be related to the influence of NAO/AO mode changes. In the late Holocene, reduced calcite deposition during historic minima of solar output is indicative of the influence of solar forcing on Alpine climate and environment. Annual growth laminae thickness, controlled by cave drip-water supersaturation with respect to calcite, primarily reflects changes in soil pCO_2 production modulated by incoming solar radiation. The preservation of high-frequency signals, and the rapid response of speleothem climate proxy series to changes in solar radiation, favor atmospheric amplification of solar variability, rather than mechanisms involving changes in oceanic circulation. In the early- to mid-Holocene, only the lower frequency components of solar variability are preserved. Periods of reduced calcite deposition roughly correspond to the ca. 10^3-yrs-scale cycles of North Atlantic drift-ice records. Lowest growth rates are recorded at about 3200 and 6800 years BP. If the lamina thickness-climate relationships assessed for the Recent (through present-day monitoring, and by correlation with 200 years of instrumental records) held also for the mid and early Holocene, these episodes were characterized by very cold winters and relatively dry summers.

  12. Solar Energy Technician/Installer

    ERIC Educational Resources Information Center

    Moore, Pam

    2007-01-01

    Solar power (also known as solar energy) is solar radiation emitted from the sun. Large panels that absorb the sun's energy as the sun beats down on them gather solar power. The energy in the rays can be used for heat (solar thermal energy) or converted to electricity (photovoltaic energy). Each solar energy project, from conception to…

  13. Solar Energy Project, Activities: General Solar Topics.

    ERIC Educational Resources Information Center

    Tullock, Bruce, Ed.; And Others

    This guide contains lesson plans and outlines of activities which introduce students to concepts and issues relating to solar energy. Lessons frequently presented in the context of solar energy as it relates to contemporary energy problems. Each unit presents an introduction; objectives; necessary skills and knowledge; materials; method;…

  14. Solar and Solar Wind Disturbance Predictions

    DTIC Science & Technology

    2007-10-11

    PPS), Journal of Atmospheric and Solar - Terrestrial Physics , 69, 43, 2007. Lockwood, M., R. Stamper, and M.N. Wild, A...doi:10.1029/2006JA011678, 2006. Kahler, S.W., E.W. Cliver, and A.G. Ling, Validating the proton prediction system (PPS), Journal of Atmospheric and Solar - Terrestrial Physics , 69

  15. Predicting Solar Cycle 24 and beyond

    NASA Astrophysics Data System (ADS)

    Clilverd, Mark A.; Clarke, Ellen; Ulich, Thomas; Rishbeth, Henry; Jarvis, Martin J.

    2006-09-01

    We use a model for sunspot number using low-frequency solar oscillations, with periods 22, 53, 88, 106, 213, and 420 years modulating the 11-year Schwabe cycle, to predict the peak sunspot number of cycle 24 and for future cycles, including the period around 2100 A.D. We extend the earlier work of Damon and Jirikowic (1992) by adding a further long-period component of 420 years. Typically, the standard deviation between the model and the peak sunspot number in each solar cycle from 1750 to 1970 is +/-34. The peak sunspot prediction for cycles 21, 22, and 23 agree with the observed sunspot activity levels within the error estimate. Our peak sunspot prediction for cycle 24 is significantly smaller than cycle 23, with peak sunspot numbers predicted to be 42 +/- 34. These predictions suggest that a period of quiet solar activity is expected, lasting until ~2030, with less disruption to satellite orbits, satellite lifetimes, and power distribution grids and lower risk of spacecraft failures and radiation dose to astronauts. Our model also predicts a recovery during the middle of the century to more typical solar activity cycles with peak sunspot numbers around 120. Eventually, the superposition of the minimum phase of the 105- and 420-year cycles just after 2100 leads to another period of significantly quieter solar conditions. This lends some support to the prediction of low solar activity in 2100 made by Clilverd et al. (2003).

  16. Durable solar mirror films

    DOEpatents

    O'Neill, Mark B.; Henderson, Andrew J.; Hebrink, Timothy J.; Katare, Rajesh K.; Jing, Naiyong; North, Diane; Peterson, Eric M.

    2017-02-14

    The present disclosure generally relates to durable solar mirror films, methods of making durable solar mirror films, and constructions including durable solar mirror films. In one embodiment, the present disclosure relates to a solar mirror film comprising: a multilayer optical film layer including having a coefficient of hygroscopic expansion of less than about 30 ppm per percent relative humidity; and a reflective layer having a coefficient of hygroscopic expansion.

  17. Solar wind models

    NASA Technical Reports Server (NTRS)

    Leer, Egil; Sandbaek, Ornulf

    1991-01-01

    The understanding of the solar wind is based upon Parker's (1958) description of a thermally driven subsonic - supersonic outflow from a fully ionized electron-proton corona. The basic physical processes of thermally driven solar wind models are discussed. Also studied are the effect of alpha particles in the corona on the solar wind proton flux. The acceleration of the solar wind by Alfven waves is discussed.

  18. Terahertz photometers to observe solar flares from space (SOLAR-T project)

    NASA Astrophysics Data System (ADS)

    Kaufmann, Pierre; Raulin, Jean-Pierre

    The space experiment SOLAR-T designed to observe solar flares at THz frequencies was completed. We present the concept, fabrication and performance of a double THz photometers system. An innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. It is the first detecting system conceived to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. One artificial Sun setup was developed to simulate actual observations. Tests comprised the whole system performance, on ambient and low pressure and temperature conditions. It is intended to provide data on the still unrevealed spectral shape of the mysterious THz solar flares emissions. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014-2016. The SOLAR-T development, fabrication and tests has been accomplished by engineering and research teams from Mackenzie, Unicamp and Bernard Lyot Solar Observatory; Propertech Ltda.; Neuron Ltda.; and Samsung, Brazil; Tydex LCC, Russia; CONICET, Argentina; the stratospheric balloon missions will be carried in cooperation with teams from University of California, Berkeley, USA (flight over Antarctica), and Lebedev Physical Institute, Moscow, Russia (flight over Russia).

  19. Solar Coronal Magneto- Seismology With Solar Orbiter

    NASA Astrophysics Data System (ADS)

    Verth, G.; Erdéyi, R.

    2007-01-01

    MHD waves in solar coronal loops, which were previously only predicted by theory have now actually been detected with instruments such as TRACE and SUMER on-board SOHO. These observations have given the solar community an important and novel tool to measure fundamental parameters in the magnetically embedded solar corona. Theory has been developed to derive detailed diagnostic information, e.g., density, magnetic field look structure, geometry, and stratifications. In this paper we demonstrate through examples of case studies how the EUV imager on Solar Orbiter can be used for solar atmospheric (coronal) magneto-seismology. Possible methods will be discussed to determine (i) if magnetic field divergence or plasma density stratification is the dominating factor in transversal loop oscillations (ii) important parameters such as the density scale heigh and magnetic dipole depth of a loop.

  20. Experimenting with Solar Energy

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2004-01-01

    Over the past 25 years, the author has had the opportunity to study the subject of solar energy and to get involved with the installation, operation, and testing of solar energy systems. His work has taken him all over the United States and put him in contact with solar experts from around the world. He has also had the good fortune of seeing some…

  1. Cool Earth Solar

    SciTech Connect

    Lamkin, Rob; McIlroy, Andy; Swalwell, Eric; Rajan, Kish

    2013-04-22

    In a public-private partnership that takes full advantage of the Livermore Valley Open Campus (LVOC) for the first time, Sandia National Laboratories and Cool Earth Solar have signed an agreement that could make solar energy more affordable and accessible. In this piece, representatives from Sandia, Cool Earth Solar, and leaders in California government all discuss the unique partnership and its expected impact.

  2. Build a Solar Greenhouse.

    ERIC Educational Resources Information Center

    Conservation and Renewable Energy Inquiry and Referral Service (DOE), Silver Spring, MD.

    Attached solar greenhouses are relatively inexpensive and easy to build; they can provide additional heat to homes all winter as well as fresh vegetables and flowers. This bulletin: (1) describes the characteristics of a solar greenhouse; (2) provides a checklist of five items to consider before building a solar greenhouse; (3) describes the four…

  3. Solar tracking system

    DOEpatents

    Okandan, Murat; Nielson, Gregory N.

    2016-07-12

    Solar tracking systems, as well as methods of using such solar tracking systems, are disclosed. More particularly, embodiments of the solar tracking systems include lateral supports horizontally positioned between uprights to support photovoltaic modules. The lateral supports may be raised and lowered along the uprights or translated to cause the photovoltaic modules to track the moving sun.

  4. Inexpensive Photovoltaic Solar Radiometer.

    ERIC Educational Resources Information Center

    Kissner, Fritz

    1981-01-01

    Describes a low-cost instrument using a solar cell as a sensor to measure both instantaneous and integrated value of solar flux. Constructing and calibrating such an instrument constitutes an undergraduate experimental project, affording students an opportunity to examine a variety of aspects associated with solar energy measurements. (Author/SK)

  5. Solar Photovoltaic Cells.

    ERIC Educational Resources Information Center

    Mickey, Charles D.

    1981-01-01

    Reviews information on solar radiation as an energy source. Discusses these topics: the key photovoltaic material; the bank theory of solids; conductors, semiconductors, and insulators; impurity semiconductors; solid-state photovoltaic cell operation; limitations on solar cell efficiency; silicon solar cells; cadmium sulfide/copper (I) sulfide…

  6. (Solar dryer. Final report)

    SciTech Connect

    Scanlin, D.

    1985-01-01

    A small solar lumber dryer was designed and constructed with the involvement of junior high students. The dryer is a natural convection solar collector similar in shape to an attached solar greenhouse. The design of the kiln is described, modifications are proposed, and the performance is briefly discussed. (LEW)

  7. Solar Job Related Training.

    ERIC Educational Resources Information Center

    Lennox Industries, Inc., Dallas, TX.

    This book contains comprehensive instruction in design, installation, and service procedures for typical solar space heat and domestic hot water systems. The book is comprised of five major sections. Solar Systems: Past and Present presents a brief look at how far solar technology has advanced. Included in this section are descriptions of over…

  8. Alternatives in solar energy

    NASA Technical Reports Server (NTRS)

    Schueler, D. G.

    1978-01-01

    Although solar energy has the potential of providing a significant source of clean and renewable energy for a variety of applications, it is expected to penetrate the nation's energy economy very slowly. The alternative solar energy technologies which employ direct collection and conversion of solar radiation as briefly described.

  9. Solar disk sextant

    NASA Technical Reports Server (NTRS)

    Sofia, S.; Chiu, H.-Y.; Maier, E.; Schatten, K. H.; Minott, P.; Endal, A. S.

    1984-01-01

    This paper presents the conceptual design of an instrument, called the solar disk sextant, to be used in space to measure the shape and the size of the sun and their variations. The instrumental parameters required to produce sufficient sensitivity to address the problems of solar oblateness, solar pulsations, and global size changes of climatic importance are given.

  10. Solar Energy Usage.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with solar energy use. Its objective is for the student to be able to discuss the broad aspects of solar energy use and to explain the general operation of solar systems. Some topics covered are availability and economics of solar…

  11. Cool Earth Solar

    ScienceCinema

    Lamkin, Rob; McIlroy, Andy; Swalwell, Eric; Rajan, Kish

    2016-07-12

    In a public-private partnership that takes full advantage of the Livermore Valley Open Campus (LVOC) for the first time, Sandia National Laboratories and Cool Earth Solar have signed an agreement that could make solar energy more affordable and accessible. In this piece, representatives from Sandia, Cool Earth Solar, and leaders in California government all discuss the unique partnership and its expected impact.

  12. Space Weather and the Ground-Level Solar Proton Events of the 23rd Solar Cycle

    NASA Astrophysics Data System (ADS)

    Shea, M. A.; Smart, D. F.

    2012-10-01

    Solar proton events can adversely affect space and ground-based systems. Ground-level events are a subset of solar proton events that have a harder spectrum than average solar proton events and are detectable on Earth's surface by cosmic radiation ionization chambers, muon detectors, and neutron monitors. This paper summarizes the space weather effects associated with ground-level solar proton events during the 23rd solar cycle. These effects include communication and navigation systems, spacecraft electronics and operations, space power systems, manned space missions, and commercial aircraft operations. The major effect of ground-level events that affect manned spacecraft operations is increased radiation exposure. The primary effect on commercial aircraft operations is the loss of high frequency communication and, at extreme polar latitudes, an increase in the radiation exposure above that experienced from the background galactic cosmic radiation. Calculations of the maximum potential aircraft polar route exposure for each ground-level event of the 23rd solar cycle are presented. The space weather effects in October and November 2003 are highlighted together with on-going efforts to utilize cosmic ray neutron monitors to predict high energy solar proton events, thus providing an alert so that system operators can possibly make adjustments to vulnerable spacecraft operations and polar aircraft routes.

  13. Radio frequency detection assembly and method for detecting radio frequencies

    SciTech Connect

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  14. Neutral hydrogen in the solar wind acceleration region

    NASA Technical Reports Server (NTRS)

    Olsen, Espen Lyngdal; Leer, Egil; Holzer, Thomas E.

    1994-01-01

    Observation of solar Ly alpha radiation scattered by coronal neutral hydrogen atoms can be used to investigate the acceleration region of the solar wind. In this paper we focus on the use of these observations to study Alfven waves, which can accelerate the solar wind plasma to flow speeds observed in high-speed streams if their amplitude at the coronal base is 20 km/s or larger. The wave amplitude is then larger than the proton thermal speed in the outer corona, so that the mean proton speed (averaged over a wave period) is significantly larger than the proton thermal speed. For low-frequency wave the hydrogen atoms follow the proton motion in the waves, while for higher frequencies the protons move relative to the neutrals. Nevertheless, in the higher frequency case, the rates for charge exchange and recombination are high enough to broaden the velocity distribution function of neutral hydrogen. Both the wave motion of the hydrogen atoms in low-frequency Alfven waves and the 'heating' by higher frequency waves lead to a broadening of the scattered solar Ly alpha line. For coronal base amplitues of 20 km/s, the line broadening increases with heliocentric distance beyond 4-5 solar radii.

  15. Quantifying Solar Wind-Polar Cap Interactions

    NASA Astrophysics Data System (ADS)

    Urban, K. D.; Gerrard, A. J.; Lanzerotti, L. J.; Weatherwax, A. T.; Huang, Y.

    2015-12-01

    It is well known that the solar wind is a major driver of ultra-low frequency [ULF] power at ground locations from low to high latitudes. However, due to the scarcity of deep polar cap magnetometer sites, it is not clear when, where, or if this is true deep inside the polar cap on open field lines where interplanetary magnetic field [IMF] ULF waves could possibly be directly detected. Given recent observations of very large Joule heating estimates from DMSP data, together with the large heating reported by the CHAMP satellite, it is important to understand the degree to which ULF waves in the solar wind can directly cause such heating. Using a time series of lagged correlation sequences ("dynamic correlograms") between GSM Bz ULF power (computed via data obtained from NASA's Advanced Composition Explorer [ACE] ahead of Earth in the solar wind) and the horizontal ULF power (H^2=N^2+E^2) from ground-based magnetometers in Earth's southern polar cap, we investigate the direct penetration of ULF waves from the solar wind into the polar ionosphere during a gamut of space weather conditions at a distributed network of Automated Geophysical Observatories [AGOs] in Antarctica. To infer causation, a predicted lag correlation maximum at each time step is computed by simply dividing the associated distance of ACE from Earth by the concurrent bulk solar wind speed. This technique helps parse out direct penetration of solar wind ULF waves from other sources (e.g., via leakage from closed field line resonances due to the bulk solar wind plasma viscously interacting at dawn/dusk flanks inducing Kelvin-Helmholtz instabilities [KHI] or compressional modes induced by impulses in solar wind dynamic pressure). The identified direct-penetrating ULF waves are related to the DMSP-derived Poynting fluxes by regression analysis, and conclusions are drawn for the importance of the ULF source for the measured heating.

  16. Solar Proton Events in Six Solar Cycles

    NASA Astrophysics Data System (ADS)

    Vitaly, Ishkov

    Based on materials the catalogs of solar proton events (SPE) in 1955 ‒ 2010 and list SPE for the current 24 solar cycle (SC) are examined confirmed SPE with E> 10 MeV proton flux in excess of 1 proton cm-2 s ster-1 (pfu) from Švestka and Simon’s (1955 - 1969) and 5 volumes Logachev’s (1970 - 2006) Catalogs of SPE. Historically thus it was formed, that the measurements of the proton fluxes began in the epoch “increased” solar activity (SC 18 ‒ 22), and includes transition period of the solar magnetic fields reconstruction from epoch “increased” to the epoch “lowered” solar activity (22 ‒ 23 SC). In current 24 SC ‒ first SC of the incipient epoch of “lowered” SA ‒ SPE realize under the new conditions, to that of previously not observed. As showed a study of five solar cycles with the reliable measurements of E> 10 MeV proton flux in excess of 1 pfu (1964 - 2013): ‒ a quantity of SPEs remained approximately identical in SC 20, 21, somewhat decreased in the initial solar cycle of the solar magnetic fields reconstruction period (22), but it returned to the same quantity in, the base for the period of reconstruction, SC 23. ‒ Into the first 5 years of the each solar cycle development the rate of the proton generation events noticeably increased in 22 cycles of solar activity and returned to the average in cycles 23 and 24. ‒ Extreme solar flare events are achieved, as a rule, in the solar magnetic fields reconstruction period (August - September 1859; June 1991; October ‒ November 2003.), it is confirmed also for SPE: the extreme fluxes of solar protons (S4) except one (August 1972) were occurred in period of perestroika (SC 22 and 23). This can speak, that inside the epochs SA, when the generation of magnetic field in the convective zone works in the steady-state regime, extreme SPE are improbable. ‒ The largest in the fluxes of protons (S3, S4) occur in the complexes of the active regions flare events, where magnetic field more

  17. Electromagnetic radiation trapped in the magnetosphere above the plasma frequency

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Shaw, R. R.

    1973-01-01

    An electromagnetic noise band is frequently observed in the outer magnetosphere by the Imp 6 spacecraft at frequencies from about 5 to 20 kHz. This noise band generally extends throughout the region from near the plasmapause boundary to near the magnetopause boundary. The noise typically has a broadband field strength of about 5 microvolts/meter. The noise band often has a sharp lower cutoff frequency at about 5 to 10 kHz, and this cutoff has been identified as the local electron plasma frequency. Since the plasma frequency in the plasmasphere and solar wind is usually above 20 kHz, it is concluded that this noise must be trapped in the low-density region between the plasmapause and magnetopause boundaries. The noise bands often contain a harmonic frequency structure which suggests that the radiation is associated with harmonics of the electron cyclotron frequency.

  18. Solar radiation absorbing material

    DOEpatents

    Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.

    1977-01-01

    Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.

  19. The Solar Maximum Mission

    NASA Astrophysics Data System (ADS)

    Chipman, E. G.

    1981-03-01

    The Solar Maximum Mission spacecraft, launched on 1980 February 14, carries seven instruments for the study of solar flares and other aspects of solar activity. These instruments observe in spectral ranges from gamma-rays through the visible, using imaging, spectroscopy, and high-time-resolution light curves to study flare phenomena. In addition, one instrument incorporates an active cavity radiometer for accurate measurement of the total solar radiant output. This paper reviews some of the most important current observational and theoretical questions of solar flare physics and indicates the ways in which the experiments on SMM will be able to attack these questions. The SMM observing program is described.

  20. Solar-terrestrial interactions

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The effects of solar radiation on man's environment are discussed. It is solar radiation that is the basic energy source driving the circulations of the earth's atmosphere and oceans. Solar radiation is responsible for the ionization of the earth's upper atmosphere to form the ionosphere, which is important to our understanding of the magnetosphere and its interaction with the solar wind. The solar wind, which is the continuous (but not steady) flow of the sun's coronal plasma and magnetic field into interplanetary space, plays both an active and passive role in its interaction with the earth's environment.